excessive brake pedal travel

HOW TO FIX EXCESSIVE BRAKE PEDAL TRAVEL

What Is Excessive Brake Pedal Travel?

Excessive brake pedal travel happens when you feel your pedal sinking rapidly while braking, or sitting lower than usual when activating your vehicle’s brakes. This can happen due to wobbly discs knocking pistons back or air in the braking system.

Performing DIY brake repair to fix excessive brake pedal travel can be a tedious task. Follow the steps below to diagnose and repair your sinking brakes.

How to Fix Excessive Brake Pedal Travel

1. Diagnose the Problem . To diagnose issues with the master cylinder, the first thing you need to do is remove the lines, install brass or plastic plugs into the outlets, and apply the brakes. What happens when you apply the brakes will tell you what issue your vehicle is having. You can continue this process of elimination by isolating each wheel.

2. Use Your Parking Brake. If you don’t typically engage your parking brake, the parking brake can be key in figuring out if your car is suffering from excessive brake pedal travel. If the parking brake doesn’t properly engage, that generally means a low pedal.

3. Bleed the Brakes. Bleeding your brakes is an important step in brake pedal travel repair and other brake issues. Use a jelly jar half full of brake fluid and a short hose to depress your brake pedal.

While depressing the pedal, rotate the star wheel to lose up the clearance. Then, go back one click when the wheel scrapes. It’s best to have a partner on hand when bleeding your brakes.

4. Bleed the Master Cylinders . After bleeding the brakes, bleeding the master cylinders is the next step. In traditional systems, you begin with the longest line in the circuit first, and go from the right rear, left rear, right front, and left the front. In diagonally split systems, the order is right rear, left front, left rear, and right front. Flush out the bleeder valves, and finally, remove the air from your master cylinder.

If you’re not sure which type of system your vehicle is or are unaware of the proper tools needed to fix excessive brake pedal travel, it’s best to bring your vehicle into Brake Works.

With two convenient locations with great weekend hours, getting proper brake maintenance is simpler than you think. Contact our team of certified specialists to schedule an appointment.

Erika Suarez

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June 2019 Issue

Abnormal brake pedal diagnosis.

By Roy Dennis Ripple

A customer may complain of a brake pedal that ‘feels funny.’ It's your job to determine whether it’s due to aerated and/or contaminated brake fluid, excessive pedal travel or any other cause.

Vehicles normally respond to our commands in a fairly predictable manner. When we push on the accelerator, we go forward; when we turn the steering wheel, we change direction; and when we press the brake pedal, we stop. Of all the things we ask of our vehicles, “please stop” is the most important request. The brake pedal should give the driver a reassuring feel that says, “I got this.”

The brake pedal is the driver’s physical connection to the brake system, providing feedback that the driver uses to determine if there’s a problem with his brakes. Spongy, mushy and squishy are just a few of the terms that a customer might use to describe negative brake pedal feedback. Sometimes these concerns can be tricky to diagnose due to the numerous failures that can cause an unacceptable brake pedal feel.

The first step in diagnosing a low brake pedal concern is to determine the type of low brake pedal issue you’re dealing with, and if other symptoms are present. It might be a good idea to forgo the road if you’re uncomfortable with the function of the brakes and settle for a parking lot cruise instead.

Besides a low or mushy pedal, note if the brakes pull, squeak or pulsate. Does the pedal slowly drift to the floor when at a stop, or does it stop solid, but too close to the floor? Determine if one or more wheels are locking up, and note if the red or amber brake warning lamps are illuminated. All of this information will aid in your diagnosis.

A low brake pedal is always caused by either a hydraulic or a mechanical malfunction. When a mechanical malfunction is the cause, it’s due to a component moving past the range of motion for which it was designed. A good example of this is out-of-adjustment rear brake shoes. The universally accepted specification for brake shoe-to-drum clearance is .015 in. Every thousandth of an inch over spec causes excess brake pedal travel. Less than .025 in. travel at the master cylinder pushrod can equal about ½ in. at the pedal. Every little bit of unnecessary movement adds up.

Another example is a caliper piston that retracts too far into the bore when disengaged. Rear calipers with integral parking brakes are notorious for this. This causes the piston to travel further than designed to initiate contact between the inboard pad and the rotor. This excess travel can translate into a heap of movement at the brake pedal.

Hydraulic concerns present the biggest challenge in low brake pedal diagnosis. The smallest amount of air trapped anywhere in the system will have a big effect on brake pedal feel. Brake fluid converts the energy applied to the pedal into the force required to engage the brakes. This happens because fluids are compressible only to a very small degree, so any pressure applied to a liquid is transferred to all portions of the liquid and to the walls of the container it occupies. Since air is very compressible, air creates a nice, soft cushion for the fluid to lean on, ruining any chance of achieving solid hydraulic pressure.

Use the information you acquired during the road test to guide your initial visual inspection. Watch all the calipers move while an assistant pumps the brake pedal. Worn caliper pins or incorrectly installed brake pads can cause the caliper to flex side to side. This lateral movement uses up brake pedal travel. Be cautious of brake pads that are location-specific, or that need to line up with a locating pin during installation. If these pads are incorrectly installed, they’ll cause the caliper to flex.

While you’re eyeballing the calipers, make sure they’re on the correct side. When a caliper is installed on the wrong side, the bleeder valve will be below the inlet. Since air rises to the top, good luck bleeding that caliper. Check meticulously for an external leak. Brake fluid leaks don’t always present themselves as drops that puddle in the driveway. Just a little seepage at a fitting can cause big trouble at the pedal. Don’t forget to look behind the wheel cylinder boots while checking for leaks; there should be no fluid there.

During your visual inspection, also watch the rubber hoses as a helper pumps the brake pedal. Look for a bulge in the hose that appears under pressure, then disappears when the pedal is released. I’ve seen hoses twist while pressurized due to a defect at the union where the rubber hose meets the metal crimp. Excess hose movement causes excess pedal movement.

Most negative brake pedal feedback issues fall into one or more of the following categories:

•A pedal that stops hard at the bottom but has excess play at the top is usually the result of a master cylinder or pushrod issue. •A pedal that’s spongy or mushy can be caused by air intrusion, contaminated brake fluid or a mechanical component moving beyond its designed range of motion. •A pedal that continues to move toward the floor when applied is caused by a loss of hydraulic pressure, which can be caused by an external leak or an internally leaking component. Contaminated brake fluid can also cause a brake pedal to drift downward.

An occasional exception to these rules—there’s always an exception—is the antilock brake system (ABS) hydraulic control unit (HCU). A defective HCU will create symptoms that feel like air intrusion or a pressure loss and can really complicate your diagnosis.

Let’s look at a brake pedal that stops hard at the bottom but has excess play at the top. A good way to determine if there’s too much pushrod travel is to loosen the master cylinder-to-power booster attaching hardware. Have an assistant hold the loose master cylinder firmly against the booster while you slowly apply the brake pedal. Determine how far the pedal moves before your helper feels the push on the master cylinder. Excessive pushrod play could be caused by a weak or broken master cylinder bore spring that’s not returning the piston all the way to the back of the bore, or it could be a pushrod or booster issue. Remember, a little play at the pushrod is a lot at the pedal.

Many automakers use an adjustable pushrod. This adjustment is set at the factory and shouldn’t have to be messed with. If you need to adjust the pushrod, something’s wrong.

We once serviced a Ford Escape with excessive brake pedal travel at the top. Loosening the master cylinder determined that we lost about 3 in. of pedal travel before the piston moved. We removed the master cylinder and discovered that the small dome-shaped piece that was pressed into the end of the pushrod, which fits into the master cylinder bore, was missing, and laying at the bottom of the booster. This added almost ¼ in. of travel to the pushrod.

Diagnosing a spongy, mushy brake pedal issue can sometimes be frustrating as well as time-consuming. Here’s an example of how important the initial road test is when diagnosing a spongy brake pedal.

While we were road-testing a vehicle with a low, spongy brake pedal, we noticed that the brakes pulled to the left. That told us that the left front and right front calipers were not applying evenly. Using the results from the road test, we started our visual inspection at the front calipers. Both front wheels were spinning freely and both stopped spinning when the brakes were applied. There was no excessive movement in either caliper or hose during brake application, and the brake pads were a healthy 9mm, with nice, beefy rotors.

Since the road test suggested there was an issue with the front brakes, it only made sense to check the front calipers for air. We removed a nice pocket of air from the right front caliper, which temporarily fixed the pedal. I say “temporarily” because we found no reason for that caliper to be holding air, as there was no sign that it was recently disassembled. Caliper piston seals and wheel cylinder cup seals can replicate a one-way check valve. Fluid can’t get out but air can get in. So we replaced the caliper. This scenario reinforces the importance of gathering information during the road test. If we didn’t feel the brake pull, we wouldn’t have started our diagnosis at the front calipers.

Unfortunately, it’s not always that simple. If you’re faced with a low, mushy pedal and the visual inspection yields no clues, it’s time to break out the blockers. Blocking off sections of the brake system (not individual components) is the surest way to find the cause of the problem. Thexton Manufacturing makes a master cylinder plug kit (Part No. 803P) that can also be used on HCUs. It’s important to use quality plugs when blocking brake pressure. A small leak at a plug will yield erroneous results.

Always start by blocking the master cylinder ports. If the master cylinder is good, the pedal should be rock hard—barely moving—with the ports blocked. If the brake pedal moves at all, the master cylinder is leaking internally, there’s a pushrod issue or the brake fluid is contaminated.

If the master cylinder is good, most diagnostic procedures recommend blocking the HCU ports next. The problem is that the HCU tends to be hard to access, and the fittings are usually tough to get a wrench on due to their proximity to each other. So in the spirit of streamlined diagnosis, it makes sense to check the easier-to-access components first, which would be the wheels.

Block each wheel individually at the steel line, before the rubber hose; this way, you’re taking the hoses, calipers and wheel cylinders out of the equation. Do not block off the calipers by using vise grips to crimp the rubber hoses. Damaging a rubber brake hose could cause it to work like a one-way valve, allowing pressure to be applied to the caliper but not to bleed off, causing a perpetually applied brake caliper. The Thexton block-off kit contains only male fittings, and you need a female fitting to block the steel line. Attaching a brass union to the male plug works great. Test the pedal after blocking each wheel. We found a right rear caliper on a Ford Explorer that was causing a low, spongy pedal using this method. We never did identify the actual cause of the caliper malfunction. It wasn't leaking, the pins were sturdy, no air, all looked fine. But the pedal came right up when we blocked it off. We replaced it; problem fixed.

If you find no problem at the wheels, you’ll need to access the HCU. It’s best to block all the outlet ports on the HCU at the same time. This is a lot of work just for a diagnosis, but at this point there’s very little choice.

If the pedal is still low with all the HCU outlet ports blocked, before passing sentence on the HCU, perform a service bleed. HCUs seem to be a favorite resting place for stowaway air. Even if you have no reason to believe that the brake system was opened to atmosphere, you should bleed the HCU before condemning it.

ABS service bleed procedures are performed with a scan tool and vary by manufacturer. Some procedures are as easy as pressing the brake pedal a few times and clicking a button on the scan tool; others will require you to open bleeder valves, which makes a real mess on the shop floor. Whatever the procedure, it’s very important to bleed all the wheels after performing an ABS service bleed.

I started using a brake pressure bleeder a couple of years ago and I’ll never go back to the old pedal-pumping method. Pressure bleeders work great. They attach to the master cylinder reservoir in place of the cap and put the brake system under consistent pressure. The biggest advantage of this—besides not needing an assistant—is that you can open a bleeder valve and just let it flow, pushing all of the air out of a line from the master cylinder to the wheel cylinder or caliper with just one turn of a bleed er valve. If you don’t already have a pressure bleeder, I highly recommend getting one.

It’s important to properly benchbleed a new master cylinder before installation. It can be tough to bleed the air from a master cylinder once it’s installed on the vehicle. Mount the master cylinder firmly in a vise and screw bleeder fittings into the outlet ports. Attach hoses to the fittings, with the other ends of the hoses in the reservoir, submerged in brake fluid. An effective kit for bench-bleeding a master cylinder comes with check valves, which allow the air to be pushed out while not allowing air to get sucked in on the back stroke. Thexton, Dorman, NAPA and others offer such kits.

If you don’t have check valves for the hoses, the procedure will still work. Since the hoses are submerged in brake fluid, fluid from the reservoir rather than air will be pulled back into the master cylinder. The problem is that air that doesn’t make it to the end of the hose gets sucked back into the cylinder on the back stroke. Check valves prevent this from happening.

With the hoses in place, slowly push the piston into the master cylinder, then allow the piston to return to the rest position. You’ll see air bubbles exit the master cylinder through the clear hoses. Do not push the piston past its normal range of motion; doing so can damage the piston seals, rendering the master cylinder useless. When using check valves, all the air is gone within seven to ten strokes. Be sure that the fittings are tight, as a poor seal at a fitting will pull air into the master cylinder.

The heart of a hydraulic brake system is the fluid, and when that goes bad, so does the pedal. Most automotive applications use DOT 3, DOT 4 or DOT 5.1 fluid, all of which are glycol-ether-based. DOT 5 is silicone-based and should not be mixed with glycol-based brake fluids. The most important property of brake fluid is that it maintains a stable viscosity and compressibility throughout its entire operating temperature range—very cold to very hot. The negative property of brake fluid is that it’s hygroscopic, which means it absorbs water.

Water in brake fluid greatly lowers its boiling point. The dry boiling point of DOT 3 is 401ºF. The wet boiling point, defined by the temperature at which the fluid boils after absorbing 3.7% water by volume, is 285ºF. Big difference. Since brake fluid temperatures at the calipers can easily exceed 200ºF, this could be a problem. The fact that water freezes also tends to complicate things a bit. This is why it’s recommended that brake fluid be changed every two years.

When brake fluid is contaminated with water it turns a darker color. If the brake fluid looks contaminated, or if you’re diagnosing a vehicle that’s more than two years old, recommend a brake fluid flush. Use a pressure bleeder or brake fluid flush machine to push all the old fluid out through the bleeder valves. Be sure to check all the bleeder valves before selling the brake flush. If you think the valves are going to break off, you need to know this beforehand.

A couple of more things: A customer might describe an intermittent false ABS activation event as a low brake pedal. But if the pedal feels fine to you, check for DTCs in the ABS module. Also, contaminated fluid can damage an HCU. Brake fluid is designed to protect metal brake parts against corrosion, an attribute it loses when weakened by water. So when replacing an HCU, it’s imperative to flush the fluid.

It seems that the furthest thing from anyone’s mind as he’s driving down the road is the brake system. The song on the radio or the setting of the climate control system occupy more brain space than the brakes do. So maybe problems like a low brake pedal and/or noisy brakes should be looked upon as an important safety warning. It’s the brake system whispering, “Hey, remember me?” to the procrastinator who should plan on getting his brakes checked very soon.

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Dealing With A Low Brake Pedal

"Honey, can I borrow your car?" No problem. She tosses you the keys. But at the first stop sign you draw a startled breath--the pedal's going, going, almost gone! There's even a little dent in the carpet under the pedal. Didn't she notice? Well, no she didn't. Typically, low-pedal trouble develops so gradually that people don't realize it.

Hydraulic brakes have been around since Duesenberg introduced them in 1921, but apparently a long history is no defense against troubles. And professionals and do-it-yourselfers alike are often guilty of misdiagnosis--they blame the master cylinder, though it is seldom the culprit.

There are only two plausible reasons for a low pedal: air in the system; and excessive movement between linings and rotors or drums (due to lack of adjustment, an out-of-round drum, or a wobbly disc that's knocking the pistons back so that there's extra space to take up before braking action begins).

Isolation You can find out all you need to know about the master cylinder by removing the lines, screwing brass or plastic plugs into the outlets, and then applying the brakes. If the pedal's high and hard now, the master has been properly bled and its seals are okay. The pedal would sink gradually if it were bypassing--that is, if fluid were finding its way around the sliding seals. You've also confirmed that the booster is okay. Reattach the lines.

Continue the process of elimination by clamping hoses to isolate each wheel. Use a suitable rounded-jaw tool, either the locking-pliers type or one of those inexpensive J-hooks with a knurled screw. Releasing one at a time should locate the problem.

Use That Parking Brake If you never engage the parking brake, self-adjustment of the pads and rotor simply won't occur, and that means a low pedal. Another impediment to adjustment is corrosion and contamination of the piston, cylinder and self-adjustment hardware. So, change your habits and start using the parking brake every time you leave the car, and overhaul or replace those calipers if they're not just right. If the parking brake isn't used regularly, one of these days a parking lot attendant will apply it and your car will be immobilized until those corroded cables and other seized parts are replaced.

Beat The Drums Rear drum brakes can cause a low pedal, too. Seized star-wheel screws and otherwise inoperative self-adjusters are practically an epidemic, and you're risking trouble if you don't replace the hardware when replacing shoes. At the very least, clean the star-wheel threads and treat them to a coating of antiseize compound.

There's another factor that's usually not recognized: drivers who never stop aggressively enough in Reverse to ratchet the self-adjusters. It's a good idea to stomp on the brake pedal every week or so while backing up--preferably in a deserted lot or other safe place.

What about the drums themselves? They're frequently out of round, leaving excess shoe-to-drum clearance and, of course, causing pulsation.

The old-fashioned, low-tech way to bleed brakes is to use a jelly jar half full of brake fluid, a short piece of hose, and a patient helper to depress the brake pedal.

Depress the tab while you rotate the star wheel to close up the clearance. When the wheel scrapes lightly, go back one click.

Brake drums will be marked clearly as to how far they can be machined safely to remove out of round.

Bubble Trouble For all practical purposes, brake fluid is incompressible. Air, on the other hand, can be squeezed down into a smaller-than-natural volume, and its presence will disrupt the operation of any hydraulic system. It promotes internal corrosion, too. Ergo, it must be expelled.

The most common cause of pedal problems is failure to bench bleed a new master cylinder. Screw the supplied fittings into the outlets and place the tips of the tubes in the fluid in the reservoir. Clamp one of the master's mounting ears in a vise--don't grip around the cylinder--so the unit is as level as possible. Use a rod or drift to stroke the piston slowly. Wait at least 15 seconds between strokes to allow the low-pressure chamber to release all its bubbles and fill completely. Keep stroking until there's no more evidence of air at the ports and tube tips.

If the car has a replacement cylinder that somebody didn't bench bleed, you might be able to do it with the master in place, provided you can jack the rear of the vehicle high enough to get the cylinder to be level. Again, pump slowly and allow time between strokes.

An important precaution to observe during any bleeding procedure that involves pumping the pedal is to limit pedal travel. You don't want the delicate lips of the master cylinder's piston seals to ride so deep in the bore that they encounter rough corrosion or deposits, which can scratch them. Just throw a chunk of 2 x 4 on the floor under the pedal.

When it comes to the bleeders at the wheels, most people just open them and let the fluid squirt. Not only will this result in slippery puddles on the floor, the fluid can shoot farther than you might expect--think about the 2500-plus psi of line pressure on some ABS-equipped cars. Brake fluid is a pretty effective paint remover, and it really burns when you get it in your eye. Wear eye protection.

One convenient setup is a tube and transparent bottle kept half full of fresh fluid. There are also inexpensive 1-man bleeder hoses that contain a 1-way valve to eliminate the possibility of air being drawn back in when you release the pedal.

The bleeder cups and hoses that are often included in manual vacuum pump kits, such as those from Mighty Vac, work well. Once again, you can see what you're getting, and you don't have to keep climbing into the seat to pump the pedal.

You should also be aware of special procedures. For example, on Teves Mark II ABS systems, you can't get fluid to the rear brakes unless you turn the key on and then apply the pedal slightly. Be sure to check the shop manual if your vehicle has an antilock braking system.

Finally, there's the bleeding sequence. Since you're supposed to do the longest line in the circuit first, the traditional order is right rear, left rear, right front and left front. But with the diagonally split systems you'll find mostly on fwd cars, the order is right rear, left front, left rear then right front. ABS-equipped cars may have special procedures to follow.

Bubbles collecting in high spots in the brake system need to be removed by opening the bleeder valves to flush them out.

Bench bleed a master cylinder to get air out before installing it into the vehicle.

How It Works: The Dual Master Cylinder

Whether you call it the dual, split or tandem master cylinder, it has been used on every car sold in this country since 1967, although Cadillac had it in '62. Even so, most people don't understand its construction and operation. A typical modern specimen is of the composite variety--aluminum with a plastic reservoir--but iron 1-piece units are still around on older vehicles. Two pistons ride in the bore, and here's where we encounter some potentially confusing terminology. The rear piston is the primary, the one in the front is the secondary. This apparent misnaming resulted because the rear piston is the first to receive the signal from the brake pedal, so it does make a certain amount of sense. Kind of. Each piston has a primary cup seal at its front and a secondary at its rear. In normal braking, the pushrod from the booster forces the primary piston forward. No pressure is created until the primary seal covers the compensating or vent port from the reservoir, but once it does fluid is trapped in the chamber between the pistons and it becomes a solid column. Pressure is routed from this chamber to two wheels. A combination of the trapped fluid and the primary piston coil spring bears on the secondary piston, to which the line to the other two wheels is attached. The replenishing ports allow fluid to move freely between the chambers behind both pistons' primary cups and the reservoir, determined by demand and expansion and contraction from temperature changes. If a hose lets go or a saboteur has sawed through one of the brake lines, the other half will still provide a means of decelerating the vehicle, albeit with a lower pedal and reduced stopping power. This protective function is, of course, the dual master's reason for being.

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brake pedal travel

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So I recently got this car and have replaced rotors and pads but not touched the hydraulics. Fluid level is good and the color is still pretty clear. The brakes work well and have decent feel. The weird thing is at a stop the pedal goes basically all the way to the floor. It doesn't just fall at a steady rate, but if I push hard after I've stopped it goes down further. It never releases the brake, the car never rolls and if I drive it feels fine. Is this normal with these vehicles or is the master starting to go on me? I know different cars have different pedal feel. Just curious what others have noticed.  

Subarus are known to have spongy brake pedal, my 3rd gen is similar. I also just replaced brakes and had a soft pedal after removing some fluid because of compressing all 6 pistons. I was worried about having to bleed them at first. After letting idle and pumping the brakes a few times it improved. Now after about 200 miles it feels great. It is still a bit on the soft side for my liking but some of that is likely firewall flex, a common complaint with all Subarus in addition to spongy pedal. There are master cylinder brace kits available to help alleviate the issue, which can get worse with spirited driving and extreme braking duties. How long ago was brake service done? Were they bled? Is it better or worse than before?  

No bleeding from me, I don't think the PO did anything. It was basically out of rear brakes when I bought it and the fronts where half gone. I'm sure the PO had pads thrown on the front and that's it.  

I've had several Subies but mostly high performance models IE STis and WRX and they've never felt quite like this. My old 99 outback is kinda crappy on the brakes but that's because they're tiny. LOL  

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How Car Brakes Work and How to Tell When They Go Bad

B rakes are your vehicle's most important safety system. Under normal conditions, a driver exerts about 70 pounds of force on the brake pedal (about the same amount of effort it takes to bite into a steak) to bring thousands of pounds of moving metal and plastic to a quick and controlled stop. A flawless brake system is absolutely crucial to driver, passenger and pedestrian safety.

Read on to learn how a modern automotive brake system works and some of the most common brake system problems .

What Are the Different Types of Car Brakes?

• All modern vehicles come with hydraulic brakes. Hydraulic brake systems pressurize and transfer brake fluid to the wheel brakes assemblies. The brake assemblies (disc or drum) use the pressurized fluid to apply the brake friction material that generates the friction needed for braking.
• Anti-lock brakes use wheel speed sensors, a computer control module and an electro-hydraulic actuator to prevent hydraulic brake systems from locking up during hard braking.
• Working in conjunction with hydraulic brakes, hybrid vehicles feature a regenerative braking system that uses the electric driveline to initially slow a car. The hydraulic brakes ultimately bring the vehicle to a stop.
• Parking brakes , independent of the hydraulic or regenerative braking system, are used to apply rear brake assemblies.

What Are the Main Parts of the Hydraulic Braking System?

Master cylinder.

When you press the brake pedal, the brake linkage (rod) pushes on the master cylinder's internal piston seals, pressurizing and forcing brake fluid into the brake lines, brake calipers and wheel cylinders. This causes the brake pads to press inward against the rotors and force the brake shoes to press outward against brake drums.

Power brake booster

Brake boosters assist drivers by multiplying the force they apply to the brake pedal. These boosters use engine vacuum, an electric pump (diesel engines produce little or no engine vacuum) or hydraulic pressure (usually the pressure of the power steering pump). This increases braking performance while decreasing pedal effort, making driving safer and more pleasurable.

Brake lines and hoses

Made of double-walled steel and multi-layer rubber and synthetic compounds, brake lines and hoses transfer pressurized fluid from the master cylinder to the brake wheel assemblies.

Disc brake assemblies

A disc brake assembly consists of a brake caliper, brake pads, disc rotor and mounting hardware.

Drum brake assemblies

A drum brake assembly consists of a backing plate, wheel cylinder, brake shoes/linings, hold-down and pull-back springs, brake drum and an automatic self-brake adjusting mechanism.

Brake switches

Modern brake systems include a brake warning lamp switch that tells the driver if the master cylinder is low on brake fluid, or there is a problem with the brake system. There is also a parking brake warning light that lets you know if the parking brake is engaged.

Parking brake

Applying the parking brake mechanically locks the rear brake assemblies to keep a car stationary when parked on a hill. It also helps stop a vehicle due to a hydraulic system failure.

A hybrid's hydraulic brakes includes all the same parts as a standard hydraulic brake system.

How Does the Braking System Work?

Hydraulic brake systems convert mechanical energy (the spinning wheels) into heat energy by transforming and amplifying the force exerted on the brake pedal. The brake pedal acts like a lever. Along with the brake booster, it greatly multiplies the force applied on the brake fluid in the master cylinder.

The master cylinder also increases brake fluid pressure, then sends pressurized brake fluid, via brake lines and hoses, to the brake calipers and wheel cylinders. The pressurized fluid acts on the caliper piston, squeezing the disc brake pads inward, clamping the pads against the brake rotors .

On drum brakes the wheel cylinders slide outward, forcing the brake shoes against the drum using a wedging, jamming action — similar to how a bicycle coaster brake works. The energy of the pads clamping against the rotors and brake shoes pushing against drums generates friction and heat. This heat-friction, along with friction generated between the tire and road surface, slows rotor and axle (and wheel) rotation and ultimately brings the car to a stop.

On a regenerative braking system, stepping off the accelerator or pushing on the brake pedal causes a hybrid car's electric drive motor to run backward. The drive motor spinning backward places a drag on the wheels and slowing the car, while also producing electricity that recharges a hybrid's high-voltage batteries. While regenerative braking provides practically all the initial stopping power, the hydraulic system engages during panic stops or hard stopping at high speeds.

Signs the Braking System Isn't Working Properly

Grinding (metal-to-metal), noisy brakes.

• Worn or damaged brake pads or shoes (possibly digging into and scoring the disc rotors or brake drums), or brake pad wear indicator rubbing against the rotor.
• Worn, rusted, missing or broken brake hardware, excess brake dust accumulation, rust build-up on rotors or drums, or a stone, rust or some other foreign object jammed between a rotor and pad.

Steering wheel or brake pedal vibrating when stopping

• Excess rotor "run-out" (thickness varies across the face of the rotor) or drums are "out-of-round," badly rusted rotors or drums, contaminated brake linings, cracked, damaged or glazed rotors or drums.

Spongy or fading brake pedal

• Low brake fluid, air trapped in the brake fluid or a leak in the hydraulic system.

Low brake, excess pedal travel

• Brake self-adjusting mechanism not working, low brake pads or shoe linings, misadjusted master cylinder push rod.

Pulling to one side when stopping

• Seized or leaking brake calipers or wheel cylinders, contaminated brake linings, faulty self-brake adjusting mechanism, build-up of excess brake dust or a front-end alignment out of adjustment.

Dragging brakes

• Weak, damaged or rusted brake hardware, seized brake calipers or wheel cylinders, collapsed brake hose, misadjusted parking brake cables or misadjusted master cylinder push rod.

Grabbing or locking brakes

• Sticking or binding brake hardware, failing or failed anti-lock wheel speed sensors, brake lining friction surfaces contaminated by grease or brake fluid or bad brake booster.

Excessive brake pedal effort

• Seized brake calipers or wheel cylinders, clogged or collapsed brake hoses, contaminated brake linings or defective master cylinder, or power brake booster vacuum, mechanical or electrical problems.

A regenerative braking system has a unique pedal feel but can exhibit all of these same symptoms.

Brakes are one of your car's most essential safety systems. Never dismiss a brake warning light or brake system problems. Disregarding brake issues can be dangerous and lead to much more expensive repairs. When it comes to your car's brakes, it's always better to be safe than sorry.

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Excessive Brake Pedal Travel

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I've come across a few others with the same issue of excessive brake pedal travel. 2013 DC, pedal slowly crept closer and closer to the floor over the past few months and I have tried bleeding at least 5 times without any improvement. I have used the 2 person method, vacuum bleeding, techstream air bleeding, nothing has made any bit of improvement. To describe it better, the pedal sinks almost all the way to the floor before the brakes grab. There is no loss of pressure if sitting at a stop light as though the MC seals where bad and allowing fluid to bypass. As with what I have read with others, 1 primer pump before braking makes it feel normal. At this point my only guess is a stuck dump valve in the ABS modulator. With the truck off, pumping the pedal will NEVER result in a rock solid pedal, not sure if this is normal? Any other car I have worked with including my wife's 2014 corolla, when the car is off you get 2 or 3 pumps before the pedal is rock solid. When hooked to techstream I can actuate all the abs solenoids and the pedal get rock hard. This leads me to believe that the problem exists int the ABS modulator or further down the line. Does anyone know which solenoids are which? SFLH, SFLR, SRRH, SRRR, SFRH, SFRR, SRLH, SRLR are the 8, I'm assuming 4 inlet and 4 dump, but which are which? The pedal acts the same when moving or stopped leading me to believe that a warped rotor or bad wheel bearing are not a factor.  

I assume you have new pads? I can't imagine anything being actually being "stuck" in the ABS and computer not registering an error. There maybe something leaking and introducing air into the system.  

There is a section in the Service Manual that details checking the Actuator Motor. It talks of activating the ABS solenoids with tech stream. This what it says in the 2015 manual. I assume it is the same for 2013 (SFRH) and ABS Solenoid (SFRR) being RIGHT Front wheel.... LEFT Front wheel LH: ABS Solenoid (SFLH), ABS Solenoid (SFLR) RIGHT Rear wheel RH: ABS Solenoid (SRRH), ABS Solenoid (SRRR) LEFT Rear wheel LH: ABS Solenoid (SRLH), ABS Solenoid (SRLR)  

Not new pads, but checked them and they still have around 50% life left in them. It's very possible something is introducing air into the system, I am not super familiar with the tundra braking system, but with the pedal being solid when solenoids are closed I'm assuming I can rule out the MC. Not sure where the accumulator lies in the equation... Thank you for the info on the solenoids, I can mess with the truck tonight and see if I can isolate the softness in the pedal to one wheels set of solenoids. As far as being "stuck" I guess my my theory is more of the valve is functioning, but not seating properly in the valve body due to rust, debris or just wear, and allowing some fluid to bypass the dump and cycle around.  

I'm in the same boat as you when i bought the truck in July the brakes felt great but have gotten softer since then. I've done stainless brake lines,rebuilt front calipers,installed OE front brake pads and did multiple bleeds with tech stream with a pressure bleeder and the two man procedure with no help.I was thinking Master or air in the ABS that i can't out with tech stream.My next step is unbolting the calipers and bleeding them in different orientations and i'm still trying to find 12mm X 1mm plugs to plug off the master to test it.With the truck off and the vacuum bleed out of the booster i still have about a 1 1/4 of travel before then pedal get hard.Judging by the size of the master that is a fair amount of hydraulic travel before the pedal gets hard but i can not get a cutaway of whats truly in this master. If you push on the brake pedal and cycle the ABS dump valves the pedal should go to the floor as it fills the accumulators in the ABS unit all four of mine acted the same so it seems like the abs unit is fine.But the last ABS i messed with was in my 97 Chevy suburban.  

Well, have not been able to isolate the issue to any one set of solenoids. For the heck of it I dropped it off at the dealer just to see what they would say. Of course they say master cylinder (saw that coming), also say that front calipers are seized (not buying that) and need to be replaced, front rotors resurfaced, new front pads, and new rear rotors and pads....to the tune of $1800 and change.....no thanks. At this point I figure I will go ahead and start with new rotors and pads, and while I am down there and really check out the calipers and seals, clean grease everything, etc. I'm assuming nothing will change, so I'll probably replace the master as well just for kicks. If nothing changes at that point, I would have to assume that the only thing left would be the ABS Module, unless there is something else in the brake system I am missing. Just frustrating that it seems so many people have what I consider to be the EXACT same issue, and I have yet to see anyone with a definitive solution.  

One thing you could maybe check is your wheel bearing... I know it's a completely different animal, but I know in the ATV world, if you have to pump your brakes to make them hard, with no air in the system, nothing else out of the ordinary, if the wheel bearing is going bad, the rotor can tend to push the caliper piston back in, then, when it comes time to hit the brakes, you basically have to "take up the slack" again. Just a thought.  

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Excessive brake pedal travel

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I've been experiencing this for quite some time now, and I need to get it sorted. So I'd really appreciate some suggestions on what I need to do/replace. Car is a '01 E39 530i. The actual braking power does not seem to be an issue, it's mainly excessive travel accompanied by a slight sponginess. However when I hold the pedal down (at traffic lights for instance), it doesn't budge - I believe if a faulty master cylinder was present the pressure would drop and the pedal would drop to the floor, but it doesn't. The brakes have been bled recently with fresh fluid (using DIS/GT1 to vent ABS valves also) as was the clutch slave. Front calipers are new and I'm running stainless steel lines all round. I even had a friend comment recently saying my "brakes aren't great" as they had to use more force/travel to get them to engage. Could the brake servo (booster) be the issue? Or could it still be the master cylinder even though it seems to be holding pressure? Thanks in advance.

My first suspicion would be air in the brake system. If a pressure flush of the system fails to cure the problem, there could be air in the ABS unit, which requires the servies of a GT1 or similar to cure.

The car makes it possible, but the driver makes it happen. Jim Levie, Huntsville, AL

Thanks for the reply. That's the thing though, I have a GT1 and followed the brake bleeding procedure outlined, which included venting of the valves in the ABS unit, so I'm very confident there is no trapped air in the system. It's a bit of an awkward one really, as I'm struggling to find out what I need to replace to cure the issue.

Are the new front calipers OEM or aftermarket? If they're not OEM, they may hold the pads slightly farther away from the rotors, and that distance has to be taken up by pressing the brake pedal farther.

Originally Posted by B4SH If anyone knows, it's this guy who knows literally nothing about everything. Originally Posted by fcvapor05 Do you even OT? The mean 401k around here is probably about $6, what with all the shiny cars and $1,000 watches and donations to get other members' Volvos running.

Originally Posted by Critter7r Are the new front calipers OEM or aftermarket? If they're not OEM, they may hold the pads slightly farther away from the rotors, and that distance has to be taken up by pressing the brake pedal farther. Not necessarily. Because if your theory is correct then anytime a brake pad starts to wear your brake pedal would need to travel farther And farther. The problem now seems to be the a sponginess feel. This wouldn't make A difference but what new brakes Re you running? When I changed my front brakes to stoptech bbk with stainless steel lines, I also used a pressure bleeder and thought I got everything out. The brakes where still spongy and took the longest time to figure out why that is. After much searching I decided to pump he brAkes while the car was off, open one of the bleeder valve and again press on the brakes hard. After that a couple small bubbles came out and the brakes are working perfectly again. It seems that sometimes pressure bleeder is not absolute, so maybe try doing it the old fashion way to see if it works before u spend big money on the booster and the master cylinder. Hopes this helps

Thanks for the replies. Originally Posted by Critter7r Are the new front calipers OEM or aftermarket? If they're not OEM, they may hold the pads slightly farther away from the rotors, and that distance has to be taken up by pressing the brake pedal farther. The calipers are aftermarket actually (NK brand, made by Scandinavian Brakes Systems) but were meant to be a direct replacement for OEM! Originally Posted by EURO M3 CSL Not necessarily. Because if your theory is correct then anytime a brake pad starts to wear your brake pedal would need to travel farther And farther. The problem now seems to be the a sponginess feel. This wouldn't make A difference but what new brakes Re you running? When I changed my front brakes to stoptech bbk with stainless steel lines, I also used a pressure bleeder and thought I got everything out. The brakes where still spongy and took the longest time to figure out why that is. After much searching I decided to pump he brAkes while the car was off, open one of the bleeder valve and again press on the brakes hard. After that a couple small bubbles came out and the brakes are working perfectly again. It seems that sometimes pressure bleeder is not absolute, so maybe try doing it the old fashion way to see if it works before u spend big money on the booster and the master cylinder. Hopes this helps I just replaced the OEM setup (324mmx30mm) with new calipers, discs, steel lines and pads, so it wasn't a BBK. The thing is though prior to this, I had already bled the old-fashioned way and it felt the same! So I decided to buy a pressure bleeder and setup a GT1 to vent the ABS valves, just to make sure I was doing it properly. I ran it at about 20psi, didn't get any air out of the brakes but did get some from the clutch slave cylinder. I guess it's no harm to try it again though, as you said it's a lot cheaper than replacing the booster and/or master. Also, just to clarify, there is only a small amount of sponginess in the pedal. In fact, if I didn't have excessive pedal travel, the slight spongy feel wouldn't even bother me. I saw this chart online, and it is referring to the booster as a potential cause for excess travel: Would you guys tend to agree or disagree with it's suggestions? I'm a bit lost at what to do at this stage!

Last edited by rpg; 08-17-2011 at 02:36 PM . Reason: Automerged Doublepost

You have replaced calipers & brake lines hoping to eliminate pedal travel & spongy feel to pedal-have you bled in the proper pattern?observed color of bled fluid(very dark signaling corrosion)? I suggest bleeding manually(two person method)followed by pressure bleed of system. If no improvement,the problem points to master cylinder/slave cylinder.By the way have you done a full system flush of brake fluid?(needed if color of ejected fluid was darker than normal).

As far as I am concerned, a "spongy" brake pedal means air in the system, and if the pedal pumps up higher between quick strokes, that confirms it. I've known internally-leaking master cylinders to cause almost "spongy" brakes, but I've never known one to pump up between strokes. Similarly, glazed pads/rotors can cause a spongy feeling, and greater pedal travel - but they don't pump up, either. On the other hand, did this issue begin with all your brake replacements? If so, are you absolutely sure your new components are matched to your master cylinder's output? This, because your pedal is low; the master cylinder may not be moving the fluid that the new calipers require/ Which makes me say both Critter and EuroCSL are correct. It's not that the pads are being held too far away though, critter, because they will always barely retract. It's just that the ratio of fluid movement between the master cylinder and the calipers may be incorrect, so more travel or incorrect brake balance is likelt to result. I use a pressure bleeder on one end, a vacuum bleeder on the other, and when I've replaced components, I throw in a few good hard stabs on the pedal for each wheel, while both systems are operating.

Last edited by bmwdirtracer; 08-18-2011 at 02:23 AM .

Chris Powell Racer and Instructor since, well. decades, ok? Master Auto Tech, owner of German Motors of Aberdeen BMWCCA 274412 German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

BMWDIRTRACER is on track when he states that a spongy pedal points to air in the system,while excessive pedal travel points to a bad master/slave cylinder.I am at a loss on this one since you have not answered my previous post,Good Luck!

Thanks to all for the replies. Yes, I bled in the pattern dictated by DIS/GT1 (i.e. begin from caliper furthest away from master cylinder and work towards it), I cycled the ABS valves on each wheel and the fluid was clean as I had only changed it last summer (approx 5-7k miles ago). I replaced the calipers on the front due to badly pitted pistons (and therefore sticking brakes) a couple of years ago and they've been working well since. I can't recall though what the pedal feel was like when I first changed them though unfortunately. It's only over time that I've realised something isn't right. The specifications of the NK brake caliper were identical when I checked. I cross referenced the OEM part number and "Manufacturer restriction: ATE" (translated from German) came up also in the notes, so I suspect they're built to OEM specs. The piston bore is 60mm just like OEM ATE calipers. OK, I just remembered something, what do you think in relation to this. When I was bleeding the brakes the last time (pressure bleed with GT1 cycling ABS valves) the pedal felt awesome during the bleeding procedure. It was rock solid (no sponginess) and it was right at the top. I remember thinking to myself "Wow, this is going to feel great now" but once I finished the job, lowered the car and took it for a drive, it felt the same as before. Thoughts?

The only thing I was suggesting with the whole aftermarket caliper statement was (first off- it was just a hypothetical, I was guessing) if say ... the piston o-ring were of a larger diameter, then the amount that the caliper piston retracts after braking would hypothetically be greater. I was just throwing up ideas to get people thinking, since answers weren't really flowing. EuroM3: I was in no way suggesting that as the pads wear, they get farther from the brake rotor. Repeat, I was NOT suggesting that.

I knew you meant what I said, critter, you're always right on the money. At this point, rpq, I'd throw a master cylinder at it, especially because of the good pedal during bleeding procedure. Bench-bleed it first. to save time later. Check the insides of the vacuum booster for brake fluid, which will ruin it. I am assuming that you're getting good fluid flow from each wheel's bleed screw during bleeding, correct me if that's not true.

Thanks guys for sticking with me through this thread, it's much appreciated. OK, I think that's what I'll do. I've managed to locate a TRW master cylinder (Part # PML364) for approx $80 delivered so I'm going to buy it. Thanks for the tip about bench-bleeding, I will do that first. I can't seem to find a cheap booster so I'll leave that for the moment. If my existing booster is contaminated with fluid I will look in a local breaker yard first for one in decent condition. Fluid flow is OK, I wouldn't say it's fast though. It's slightly better coming out the fronts than the rears. With the nipple open, the flow from the calipers is quite slow with just the pressure bleeder (~20psi), but once I depress the pedal to the floor about 8-10 times, I can get approx 100ml brake fluid into the bleeder bottle (from each caliper).

Update - and it's not a good one. Fitted a brand new TRW master cylinder today and a used brake booster (came from a '02 530i) from a local breakers. Everything went relatively well, and like before when bleeding it felt good. Took it off the ramps and for a drive... nothing has changed. Pedal felt stiff when pumping and bleeding but then when everything came off and put back on the road it's back to the way it was before i.e. excessive travel. I can pump it up three or four times and it will feel solid for a second, but if I hold the pedal in position, it just slowly drops halfway down (doesn't reach the floor). I really am lost at this stage. Any suggestions appreciated. Also, my 3 brake lights are on all the time now, The 2nd I turn on the car they go on and won't go off. But I'll fix that I'm sure, as it was working fine before hand.

Unfortunately for you, brake boosters cause excessive effort/a very hard pedal. Not excessive travel. That was a waste of money. Did the pedal feel spongy with excessive travel before pad and rotor replacement? It's possibly soft frictional material is slightly compressing when force is exerted, giving that spongy feel. I've also heard of instances where they develope a tapered wear, causing the pads to shift a bit when applied and pedal feels spongy. Also, I have a question. You say while you are bleeding, the pedal feels firm and is at the top. When you go for a test drive, it feels spongy with excessive travel. Are you bleeding with the engine off and feeling a firm pedal, and then starting the engine and feeling a soft pedal? That would only mean that the brake booster was working, and again was a waste to replace.

Originally Posted by jriv Unfortunately for you, brake boosters cause excessive effort/a very hard pedal. Not excessive travel. That was a waste of money. Quick, and to the point. To be honest the master cylinder was the real job today, I only replaced the booster as it had to be removed anyway and I got it for 30 odd quid, so not too much of a loss! Originally Posted by jriv Did the pedal feel spongy with excessive travel before pad and rotor replacement? It's possibly soft frictional material is slightly compressing when force is exerted, giving that spongy feel. I've also heard of instances where they develope a tapered wear, causing the pads to shift a bit when applied and pedal feels spongy. That's a good question, and unfortunately I can't remember. The pedal was never right at the top, but I don't think it travelled as far as it does now. Discs are not OEM, nor are the pads. The pads are EBC YellowStuff, they're a fast road/track pad. Originally Posted by jriv Also, I have a question. You say while you are bleeding, the pedal feels firm and is at the top. When you go for a test drive, it feels spongy with excessive travel. Are you bleeding with the engine off and feeling a firm pedal, and then starting the engine and feeling a soft pedal? That would only mean that the brake booster was working, and again was a waste to replace. Yes, bleeding with the engine off. Are you alluding to the fact that I may actually be experiencing normal brake system function?? Can I bleed with the engine on? I'll try anything at this stage!

The point is the reason it is firm and to the top is because the brake booster is not able to operate with the engine off. Here, see for yourself. Cut the engine off, and then pump the brake pedal several times. You will notice the pedal gradually getting hard. We could have chased an anomaly that doesn't exist! Was already breaking out my theories considering pressure differential when using pressure bleeder vs atmospheric pressure Now that you tell me they are race pads and rotors, I have another expirament for you. Try getting them hot, take the vehicle for a nice joy ride and put your brakes to work. I wonder if these pads true characteristics are when they are smoking hot, and here you are playing with it while it is cold, damp and unexcited! Haha take it for a test drive and let them heat up a bit, come back and tell me if that makes a difference in pedal feel whatsoever. I doubt how that would effect pedal travel too much but I'm not exactly sure what your definition of excessive travel is. Perception is everything so lets start with the basics and maybe we can help you come to a conclusive solution.

Oh, hell. I mentioned this early on, but it got away in the search of other things. Um, did you follow a good bedding procedure for the new pads? Hard pads require a thorough bedding, and I'd have to wonder whether you've just glazed the pads and rotors? You might like to go scuff the rotors and pads with 120 grit sandpaper, and rebed them gradually, and 'til they've been fully hot.

Thanks for the replies guys, but I'm very close to giving up on the whole thing. When I got the pads initially I found it very difficult to bed them in properly on the road, and as a result was experiencing brake judder/vibration through the steering wheel. Once I brought the car to a track and gave them a good run-in, the judder disappeared and they felt better. My definition of excessive pedal travel is 2-3 times the travel of that of a 'normal' car. My father's GS450h for instance bites right at the top of the pedal, mine travels nearly three times that distance before it bites. When it does, braking power is good however, there are no issue there. I guess you could say because it takes so long to bite, that it's 'spongy' up until that point. I don't know, maybe it's a combination of the new calipers, pads and discs (none of which are OEM) but I think I'm just going to have to live with it. I have been contemplating a new front brake setup for a while now (as my 530i is S/C'd) so maybe I'll just wait until I do that.

Every (newer) nissan I ever driven had very little pedal travel before the pads grab. Nearly throw myself to the windshield everytime I step on the brakes lol. There might not even be a problem if you are comparing it to that, I still think your perception of excessive travel is different from mine. If it doesnt feel excessive to the point it seems dangerous to drive on highways, but as you say brakes well then it may be normal on your vehicle.

Last edited by jriv; 09-09-2011 at 11:08 AM .

Had similar issue, now resolved.

Originally Posted by rpg Thanks for the replies guys, but I'm very close to giving up on the whole thing. When I got the pads initially I found it very difficult to bed them in properly on the road, and as a result was experiencing brake judder/vibration through the steering wheel. Once I brought the car to a track and gave them a good run-in, the judder disappeared and they felt better. My definition of excessive pedal travel is 2-3 times the travel of that of a 'normal' car. My father's GS450h for instance bites right at the top of the pedal, mine travels nearly three times that distance before it bites. When it does, braking power is good however, there are no issue there. I guess you could say because it takes so long to bite, that it's 'spongy' up until that point. I don't know, maybe it's a combination of the new calipers, pads and discs (none of which are OEM) but I think I'm just going to have to live with it. I have been contemplating a new front brake setup for a while now (as my 530i is S/C'd) so maybe I'll just wait until I do that. I wanted to resurrect this thread to hopefully help others encountering this problem. I was experiencing the same issues after a recent caliper swap out. Excessive pedal travel. Similar spongy feel. I had plenty of braking power when the pedal finally engaged. I also noticed that the car was not pulling to one direction or the other while braking, which I have noticed in the past when dealing with air in the brake system on pervious non-BMW vehicles. It turned out that the problem was actually quite simple and perhaps easy to overlook. The SPRING CLIP on the new caliper was not installed correctly. Apparently there are two ways you can install it and have it stay in. The way it was incorrectly installed did not provide enough tension to prevent the caliper piston from retracing too far back inside the caliper. This caused all the symptoms and I could visually see excessive movement while my helper engaged and released the brakes. Reinstalling the spring clip correctly solved all the issues and the car was back to normal at no cost. I hope this helps someone else down the line. It can really boggle your mind for quite awhile thinking of all these complex possible problems that may or may not fix it. I felt foolish for installing the clip wrong but overjoyed when discovering how easy it was to fix.

Are you talking about the spring clip that keeps the outer pad from rattling? I'm having a hard time picturing how that clip would limit the lateral movement of the caliper.

Same issue here that OP has. Bought my 2002 530i with 75k miles a month ago. Had spongy pedal but had aftermarket drilled/slotted rotors and who knows what pads and who knows how old the fluid was. I rebuilt the calipers, installed Zimmerman rotors, Akebono ceramic pads, FCP brass/SS slider pins, FCP SS flexible lines, and pressure bled and buddy-bled brand new ATE Super Blue fluid. Same brake feel after bedding the pads in with 10ish 50-10mph hard decelerations. Took it to my local BMW specialist shop and had them bleed it as I thought I might have introduced air into the ABS pump. They bled it with their BMW computer diagnostic system (activates the ABS pump) and bled it another way (not sure if buddy-bleed or pressure) and pushed through two more quarts of fluid. They said there is 0% chance any air is left in the system and I believe them. The owner was my service writer and he said he's driven the E39 on and off since they came out and the pedal should NOT feel like this. They even thermal imaged the brakes and found that the heat signatures and differentials were appropriate, indicating that no caliper was sticking or slow to engage/disengage. I replicated this with my infrared thermometer and came to the same conclusion as well. - With car off, the pedal is rock hard. - With car on, the pedal engages relatively early, but requires most of the travel to get full engagement, it seems a the braking force gets exponentially stronger as i push, but it's not that far off of a linear pressure application. - If I pump the brakes with the car on, the brakes DO NOT get better - brakes will engage strong enough to engage abs The shop said this does NOT seem like it is a master cylinder issue. I agree as if that were the case the pedal would continue to travel as fluid leaks out of the cylinder bore back into the reservoir or externally. The shop said this does NOT seem like the sometimes occurring contaminated brake booster issue, as mine is not full of water and I don't get any 'slushy' sound when i engage the brake pedal. My car runs fine aside from a very slightly erratic idle when cold. And if it were a booster issue, wouldn't the braking effort get GREATER? The shop said there seems to be no issues with any of the hydraulic lines as they can inspect them as well the brake thermo-imaging indicates all four corners are working properly related to one another. I do have a missing caliper pad clip on the left rear, which I will replace, but I would tend to agree with Critter that this doesn't seem like a likely culprit. I have a new set of rear clips on order and will install those this weekend. Fingers crossed I guess since I have no other idea what could be wrong here. The shop did suggest I buy some OEM or good semi metallic pads and install them dry, start the car, and apply the brakes. If the pedal feels better, ditch the Akebonos. If the pedal isn't better box them up and return them. They agree the Akebono ceramics don't offer the most positive engagement, but have never installed them to find they result in this type of symptom. So not much help here, just another E39 owner with a very, very similar situation as the OP.

Last edited by frknvgn; 11-03-2016 at 05:03 PM .

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Brakes - Excesive Pedal Travel, HELP!

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I have an '02 6 cyl FWD. I 've recently noticed there is excessive brake pedal travel, goes all the way to the floor, when braking. The fluid level is fine, just below Max. I also checked the front pads they are fine, probably between 50-75% remaining on the pads. I have not bled the brakes as there should not be a reason for air in the lines. Anyone have any ideas?  

pedal I would suspect your brake master cylinder, but I would still suggest bleeding, but you are right, it's unlikely air would just now decide to enter. I assume you have checked for leaks around your disk brake calipers?  

lqueral said: I would suspect your brake master cylinder, but I would still suggest bleeding, but you are right, it's unlikely air would just now decide to enter. I assume you have checked for leaks around your disk brake calipers? Click to expand...

I have a 2004 - It has always done it  

master . The only thing about a leak is that the fluid was not that low. How tough are master cylinders to replace on a Highlander?[/quote] The master can be leaking internally, past the piston seal, so fluid would not actually escape to the outside. I haven't done a HL master, as mine is an 05 with 22k, but it should be straightforward, although there can be some special bleeding procedures to follow or the piston inside the master might not end up centered within it's bore, leading to perhaps a brake or ABS warning light. If you explore this forum, there are service manuals for HL's available for dloading, and I would recommend that you follow the bleeding procedure described within.  

ajwilkens said: I have an '02 6 cyl FWD. I 've recently noticed there is excessive brake pedal travel, goes all the way to the floor, when braking. The fluid level is fine, just below Max. I also checked the front pads they are fine, probably between 50-75% remaining on the pads. I have not bled the brakes as there should not be a reason for air in the lines. Anyone have any ideas? Click to expand...

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Brake Pedal Travel

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I just replaced pads and rotors on my son's 01. The brake pedal seems to have way to much travel in it compared to the other vehicles we have. I checked the brake cylinders for leaks - none. The only thing I can think of is, 2 years ago he was in the DC area for the summer and the front caliper chocked and we had to have a shop replace. I am beginning to think they didn't bleed them properly? I asked him when the excessive travel in the pedal started and he he doesn't recall. I am thinking I'll bleed them again and see if there is an improvement. My other though is the master cylinder is going bad? Any thoughts/past experience on this matter? Thanks, Tim  

If I'm going to replace the pads and rotors I'll also replace the calipers, especially living in the salt/rust belt. I did a complete brake job on my 04 about 5-6 years ago then had to replace the front calipers, pads, and rotors again last year mainly do to the right front caliper locking up. When doing the first caliper replacement I let the master cylinder go dry which was likely a mistake. In using my Motive power bleeder and manual bleed procedures I had one heck of a time getting all the air out of the master cylinder. At least I bled all the old fluid out while adding new but have never seen so much of a problem getting the trapped air out of the MC. Did a master cylinder bench bleed about 3 times off my WJ then finally ended up doing a bench bleed while it was attached to the brake booster. Believe I'd start by bleeding all all the calipers and pushing all the old fluid out while never letting the MC reservoir go dry. Good luck.  

The OP's vehicle may be old enough for rubber brake lines to collapse, interfering with return pressure? My '98 developed that issue a couple years ago, so it may be time for the OP to replace rubber hoses.  

Try bleeding it first making sure all air is out of the system. If you still have a low pedal, replacing the master cylinder is good advice.  

Are your rear brakes disc or drum? As I recall the WJ could come either way. If it has drums, your rear shoes are probably out of adjustment. That causes a lot of pedal travel.  

This. ^^ Check your rear brakes whether or not it's drum or disc.  

On mine the rears are disc. I believe it does have rubber brake lines but I did take a look at them when I was in each wheel area and they looked OK but who knows when under pressure. I am going to bleed them and see what happens, if it doesn't resolve it I'll move to the next step. Thanks guys for all your input. I'll update on this as I go. Tim  

plimbob said: On mine the rears are disc. I believe it does have rubber brake lines but I did take a look at them when I was in each wheel area and they looked OK but who knows when under pressure. I am going to bleed them and see what happens, if it doesn't resolve it I'll move to the next step. Thanks guys for all your input. I'll update on this as I go. Tim Click to expand...

I had a bad ABS module. The mechanic replaced it with a used one. The pedal now travels a long way before the brakes catch. They thought that the master cylinder was bad, so they replaced that. The pedal travel is still so long it feels more like a clutch pedal. They said that they bled it 3 times with a scan tool to operate the ABS pump while bleeding. What can I do to fix this?  

You've added a new question to someone else's thread. While not a horrible thing to do, it's probably best to make your own if you can. Otherwise, we'll need more info such as ...what vehicle is this for?  

I have a 2001 grand cherokee with a 4.0L. Sorry about hijacking someone's thread. Sent from my SM-G781U using Tapatalk  

b 4 and after brake work and bleeding as good as i can, my pedal has always been soft. car stops great so i call it ok. check rotor temp with ir gun after coasting to stop. all about the same,not hot!! i find a place where i can drive ? a mile with no brakes. coast to stop. rotors should be cold...no drag.  

If it is the master cylinder it will get worse and you will have to change it. If the vehicle stops fine now it may be ok. I don't think WJ's have excessive brake pedal travel compered to other vehicles.  

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Brake pedal travel

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Have a 2011 Heritage The rear brake pedal has way to much travel , I know this is a problem but what is the fix for it.  

Does your bike have ABS ?  

no it don't have ABS  

My 2011 Heritage has ABS Sent from my SM-G900V using Tapatalk  

OK then I would try bleeding the rear brake at the caliper.  

was thinking of that but don't know how air would get in unless fluid is low I don't see a leak Going to switch out the fluid when I try this I see it is needed every 2 years  

Someone could have changed the brake light switch and gotten air in the system.  

Plenty of material left on the rear pads? Is the caliper freed up and operating normally?  

Check your pad thickness. It can be done on the bike with a flashlight and some contortion or mirror. I forgot the spec. HD uses for min. thickness, but it is about the thickness of a credit card! I replace mine way before that.  

I don't know if you bought a used or new Bike or how many miles the Breaks have on them. Most people use the Rear Break to stop. Me I use the Front because it's a lot easier to replace the PADS in the Front. Anyway to much travel is the first sign you need to check the Brake Pads. Probably your a few miles away from hearing the Rotors grinding. First I would Pull those Pads off and check them. When Harley assembles the bikes they put the right amount of Fluid in the Reservoirs, as the Break Pads ware the Fluid level will go down in the Reservoir causing Travel. If you fill up the Reservoir and you need new brake pads, you will not be able to compress the Brake Caliper Hydrophilic Plunger. Also to accomplish that task use a big C Clamp. That's what I would do, Good Luck!  

Ok I changed the fluid in the rear brakes and used a brake bleader pump on it. I have brakes I did notice when the pump was sucking out the old fluid that a single air bubble Had to be the problem How it got in there thow I have no clue. Thanks guys It a easy fix and now ill be changing the fluid out once a year The fluid was bad looked stringy I know I have never changed it in the 3 years I had the bike. Now should the front fluid be changed also It works fine but is old fluid also. Thanks again for the advice and tips  

Yes do the front and avoid problems down the road.  

Harley spec is to change fluid every 2 years. There's even a note about it related to the abs recall, that if brakes are not flushed every 2 years, the abs recall is basically voided (may have this wrong, so check the info for yourself). If you've owned the bike for 3 years, then change the front fluid and check pads while you're down there. From my 2014 service manual, min pad thickness is 16 thousandths. Eff that, that's way too thin! Sent from my SM-G950U using Tapatalk  

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Long brake pedal travel after new install

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• Feb 9, 2021

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There are numerous (hundreds?) of threads on this website about your exact problem. I would never consider installing a booster on my '65.  

That's because there's a lot of badly designed conversion kits out there. Have you ever seen a thread were someone has these problems on a Mustang with the original factory power setup? Power brakes have worked perfect on endless millions of factory made cars since the 60s. It also works perfect on my '65 with stock KH discs. Using the brakes feels like those om my modern daily driver, with similar force and travel on the pedal.  

I did the CSRP kit on my 1966, I already had a power booster so I was used to a softer pedal. I too have what seems like more travel, but they stop great, I just have to get used to it. A question what is your pedal height from the floor? I looked all over and found different answers and like a dumb a## I didn't measure before hand. Dennis from CSRP was awesome, he was very helpful and answered all my dumb questions. Even sent a replacement part next day for one line, thatI could not get to work.  

When you installed your new power brake pedal did you install it in the drum brake location or drill a new hole at the top of the pedal bracket?  

GT289 said: Pressures are good. You're to be congratulated for actually using pressure gauges..... What are the caliper piston sizes? ex-Global West GM 1991-1995 Click to expand...

If there's a lot of travel before the MC starts to generate pressure, you need to find where the slack is. If its just a general long pedal travel there's a mismatch in the combo of parts. A correct designed power brake system makes all the needed pressure with nearly half of the pedal travel of a manuel brake system.  

Pressures are good. You're to be congratulated for actually using pressure gauges..... What are the caliper piston sizes? ex-Global West GM 1991-1995  

You should be able to just use a larger master cylinder and reduce travel that way(probably a negligible pedal feet increase as long as you keep it reasonable) though I am not entirely sure how much that will affect pressure readings. I suspect a 1" master is the main problem with most of the kits out there...an a 65-66 people go from the fruit jar 1" MC with manual brakes and then go to a 1" MC with power brakes and wonder why their pedal travel is so long.  

From everything I read my problem seems indicative of too small MC bore size, even though 1" was used stock and what pretty much all the kits come with. I wonder if the larger pistons on the Wilwood calipers don't work well with the 1" MC bore?  

So this isn't scientific by any means, but I took a video of the pedal travel with the engine running . The centerline of the pedal pad travels about 2.5" measuring from the floorboard. Maybe this is just how stock power brakes were back in the 60's and I'm used to modern cars where the pedal grabs higher?  

Rear Brakes  

Yeah I think I will take the car out and do the reversing procedure to be 100% sure the rear drums are adjusted. Will see if that improves pedal at all.  

I think my next step would be to re-check the rear brake adjustment... also wondering if there is a residual valve in the rear circuit or, possibly, if the front needs a 2# one....  

Yeah I'm wondering if a lack of RPV in the rear brake circuit could be part of the problem. I can't find any specs on my master cylinder to say whether it definitely has a residual pressure valve on the rear brake port or not. It's an OEM replacement for a 68 Mustang/Cougar with power disc/drum, so it SHOULD have one. But of course that doesn't mean it actually does.  

So after the hardware I was waiting on arrived, I finally got the new parking brake cables adjusted up snug. Strangely enough, that seemed to have a positive effect on the brake pedal feel. It's not 100% where I'd want it, but it definitely improved. I think at this point I'll leave it and drive the car for a while to get the new pads/rotors/drums/shoes bedded in and then see where it ends up. Thanks for the helpful advice from everyone on the thread!  

Rear Brakes.  

You could expand upon that reply a little bit Dan? I would never count on backing up to set my rear drums. Tire off the ground, and axle supported by a jack stand, I use a brake adjustment "spoon" I think they call it to set the rear brake to a slight drag. When you think you have a slight drag pump the brake pedal a few times and see if you still have the slight drag. You may have to repeat the procedure a few times to get the shoes fully adjusted. I had to adjust the rear brakes after every autocross event on my car to have a barely comfortable pedal, but thats a car using a LOT of brake and never backing up. I'm in the process of installing a new 9" rear end with Explorer disks, but not sure that was a good idea.  

The aftermarket "commie" brake boosters don't help matters either. I've got a 7" single diaphragm booster on my 65 and while it will lock up all 4 it's got a lot of pedal travel before it does so. I have to warn my rice burning friends before I let them drive my car at events or they end up eating a lot of cones in the first corner!  

Nailbender said: The aftermarket "commie" brake boosters don't help matters either. I've got a 7" single diaphragm booster on my 65 and while it will lock up all 4 it's got a lot of pedal travel before it does so. Click to expand...

I recently went through 3 different master cylinders from 3 different vendors until I got one that looked decent and had residual value in it. You said you used a Dorman M71248, looking at your photo the universal casting looks identical to the one on NPD website for your application, the same one I received, and the same one they sell through Summit. Point being, the one I got from NPD did not have a residual value in it, so I bought a Raybestos MC36251 through Summit and it came directly from manufacturer with more of a traditional casting and a residual value installed.  

67frankenstein said: I recently went through 3 different master cylinders from 3 different vendors until I got one that looked decent and had residual value in it. You said you used a Dorman M71248, looking at your photo the universal casting looks identical to the one on NPD website for your application, the same one I received, and the same one they sell through Summit. Point being, the one I got from NPD did not have a residual value in it, so I bought a Raybestos MC36251 through Summit and it came directly from manufacturer with more of a traditional casting and a residual value installed. Click to expand...

He used a Dorman M71248 and "I think" that is also the one NPD sells as their own in-house master cylinder, so it is correct for the application, but the one I received from NPD did not have a residual valve and a crude casting, which is why I didn't use it and went with a new Raybestos 36251 with residual valve and had no issues.  

Good possibly this a somewhat of a cause in this issue??  

Going crazy with this exact problem myself ( topic here ) on an automatic 65 mustang that came stock manual drum all-around. A good 3" of pedal travel before it engages... Will be interested if you find a solution. The conversion kit I used is here . To the point a few other posters made, the kit I bought doesn't include anything on changing the pedal ratio, while the Mustang Steve kit does, so I'm wondering if that could be it...  

If you change the ratio by having a longer leverage arm (the pivot point to pedal pad distance), the effort must decrease and the length of your pedal stroke must increase. ex-Global West GM 1991-1995  

So it's official, the Dorman M71248 master cylinder does NOT have a residual pressure valve in the brake port that feeds the rear brakes. Looks like I'll be swapping out for that Raybestos master cylinder...ugh. My back still hurts from the last time having to climb under the dash to loosen the booster.  

why not just add a 10lb rpv in the lines to the rear brakes ?  

There's no room to work around the distribution block with the booster in place. If I get into modifying those brakes lines I think the booster would have to come out entirely.  

Now I'm throwing a curve in this situation. Yes about residual valves. All 67 thru 73 Power Disc masters had a 10 pound residual in the front port of the master (rear brake source). It worked great, todays new MC 36251 has the residual to maintain the 10 pounds of pressure in the line to keep shoes up to drums. Fast forward. All 74 Mavericks with front disc, rear drums used a MC 36440 master from the factory. The 440 has no residual in the front port--Yes brakes were great. The rear brakes are totally reliant on the shoes being close/against/rubbing the drum for minimal movement to make braking action. This is why that 10 pounds of line pressure keeps them close. No residual line pressure, s wheel cylinders retract, of course shoes as well, when we let off the pedal--No more pressure. Then the next push, you have to push that same fluid back there again. So, it all boils down to rear brakes being up to par, adjusted correctly, correct parts, etc. Then the residual is less effective as the shoes are already against the drums. I'm betting a 10 pound residual in this might help, But I'd review the rear drum adjustment, parts, etc. Install a residual CLOSE TO THE MASTER/Distribution block.  

CHOCK said: This is why that 10 pounds of line pressure keeps them close. Click to expand...

CHOCK said: Then the next push, you have to push that same fluid back there again. Click to expand...

Ok so got the Raybestos MC36251 master cylinder, it does indeed have a residual valve in port for the rear brakes. Gonna try and install this weekend, so should know soon if it improves the pedal feel. Thanks 67frankenstein for that tip!  

Ok so finally got around to swapping in the Raybestos MC36251 master cylinder. Turns out that residual valve makes all the difference. I've only bench-bled the master, haven't even bled the lines yet and I can already tell it's better. Took it around the block and the pedal is responsive much higher up in the travel, it feels like a typical power brake system now. Will report back after I bleed the whole system and go for a drive, but I think this was it.  

When I returned my Master Cylinder to NPD the reason stated was "no residual valuve in rear brake port" so hopefully they catch on, just think about how many of those Dorman units they have sold and people installed on their cars.  

I got mine from West Coast Classic Cougar, who normally do a great job of weeding out poor/incorrect products from the good ones. But yeah I wonder how many people put these things in their cars and just think that's the way the brakes feel on a classic car. After bleeding at the 4 corners and adjusting the rear brakes with reversing method a few more times for good measure, brakes now feel really good. This was a PITA but I'm glad to have the brakes working and feeling the way they're meant to. Thanks everyone for the help and advice!  

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Excess brake pedal travel

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This topic may have been covered numerous times, but with the new sucktastic forum software that won't let us seach individual forums, who know? Anyway, my brake pedal feels like you have to push it 1-2 inches before the brakes grab. I had my local shop look into it. They said the brakes worked normally once you push through the dead travel range. No issues with the fluid or vacuum. They said they think there might be some mechanical adjustability in the brake pedal mechanism, but they weren't sure. Has anyone else experienced a "dead zone" in their brake pedal?  

Yes, my 1995 SL320 has the same problem. Checked by my MB mechanic and found no obvious problem with brakes. However, I do not believe this to be normal for the brakes. My 1985 500SEL brakes respond at a much higher, normal pedal.  

I own a couple of W210s and have owned four W124s and a W201. None of them exhibit the long travel before engagement. I resorted to using google to search this forum, and found a previous thread. Sounds as though it is a common R129 "quirk." Brake Pedal Travel  

Check the brake master cylinder.  

I have this very same problem. I purchased SS brake lines, a brand new master cylinder and brake booster that works on the SL500/SL600 until MY98. After that the brakes were perfect to the touch. However, I traveled for a week and when I came back, I found the brakes suffering from dead travel again. Every time I bleed the brakes, they feel good but not great for a day or so and then they get spongy again. Maybe I have an internal problem in one or more of my calipers. My next target to solve this and get better braking would be to update to the 99+ brembo brakes and silver arrow rotors with 99+ SS brake lines again from Goodrich.  

Just to let you know, I upgraded to the Silver Arrow cross drilled zimmerman rotors and techstar pads. No change in travel.  

Do you have steel brake lines or the oem rubber ones? The reason I'm expecting a change in travel is because I think there might be something wrong with one or more of my calipers. After bleeding them, they would feel good for a day or two, then they start feeling spongy again and need re-bleeding. That is my assessment since everything else is brand new. And if I was to change the calipers, might as well get the upgraded Brembos. Isn't your car a 1999 model? You should already have the big brembo calipers with 234mm brake disc upfront and 300mm in the rear. My 1991 has the smaller 300mm upfront and 278mm in the rear. So I should feel more of a brake upgrade when changing.  

Excessive brake pedal travel is an inherent issue with the R129. This was a very common complaint at the dealerships when the R129's were new. I had a 1995 SL500 years ago, same issue. Thorgod  

Thorgod said: Excessive brake pedal travel is an inherent issue with the R129. This was a very common complaint at the dealerships when the R129's were new. I had a 1995 SL500 years ago, same issue. Thorgod Click to expand...

Click on the 3 vertical dots on the top right of the page and you will see the Search feature for individual forums.  

Of course! Perfectly intuitive! It isn't. Thanks for the tip.  

For what it's worth I just had my brakes refreshed with new fluid, SS lines, EBC red pads, and Zimmerman rotors. This significantly reduced my brake pad travel and improved feel.  

This past weekend I finally got around to putting new brakes on the '99 SL500: Zimmerman rotors and Akebono pads. The dead travel seems to be gone now. What isn't gone is is the mushy feeling and the lengthy pedal travel. At least I can now feel the brakes grab before the pedal travels an inch or two. I don't know why M-B designed the SL's this way. All the other Benzes I have owned had a really firm pedal feel.  

Mine possesses none of those issues. The symptoms you describe typically come from poorly bleeded brake lines/water in brake fluid.  

my 97 R129 and 97 E420 have ENTIRELY different brake feel. E420 has very short travel but not easy to modulate. R129 has long travel and is very easy to modulate. Later models had "brake assist" that with fast application increased brake pad pressure. The tradeoff is do you want "instant" brakes that are hard to modulate or brakes that can easily be modulated, or something in between. I'd like something in between.  

I have a W210 E430 and a 1996 R129 SL500 so I know exactly what you mean ;-)  

Obviously no one can know how your brake pedal feels; when I got my SL 8 years ago I was aware of a long travel before the brakes caught; now I don't even notice it.  

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Excess Brake Pedal Travel?

• Thread starter PDJetta
• Start date Jul 19, 2012

Top Post Dawg

The brake pedal on my '04 always seemed to have too much travel before the brakes engage. Its like the brakes are out of adjustment (they are automatic adjusting, though). I would estimate the brake pedal travels 2-3 inches before the brakes begin to apply. This equates to about half of the total posible pedal travel before bottoming out on the floor. I think the pedal has been like this from day one. I bought the car new. In contrast, the pedal on my mother's '00 Jetta TDI engages the brakes after a half of an inch or so of travel and she even commented about how poor my brakes felt when driving my car. I flush the brake fluid every 2 years with a power bleeder and I even ran the VCDS antilock brake pump procedure to purge all possible air. No change whatsoever. Other that that, I have no idea about what to do, other than replacing the master cylinder. All brake components are original, car has 150,000 miles on it. The car does seem to brake fine, though, and the pedal, although a little soft, the car will stop adequately on hard braking. Its just a little unnerving with the brake pedal having so much travel before the brakes apply. Does this seem normal? If not, any idea what to check? Thanks. --Nate  

I can give a little bump and say that mine is not more than 3/4'' before the brakes apply. So I agree, not normal.  

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Mine like yours has been like that since day one. I like you performed all the same procedures. The two things that finally helped were: 1) Adjust parking brake by: pump brakes 5 times in 4 seconds, hold then pull firmly on the parking brake lever, release foot, release hand brake and repeat 5 times. I try and do this at least once/month. 2) After 50k mi. it dawned on me that I hardly ever really apply the brakes hard and in fact they have never really been seated properly. I went ahead and applied the standard brake seating procedures and both these tasks have greatly improved the confidence of the pedal. I went out on an empty hiway, ran it up to 60mph and panic near-stopped on the brakes, enough to activate the ABS. I did this about 5 or 6 times. This flushes fluid thru the pump and heats the pads to the disc. Now (summer) is a good time to bed the brakes.  

Thanks.. "After 50k mi. it dawned on me that I hardly ever really apply the brakes hard and in fact they have never really been seated properly." I brake VERY lightly almost all the time too. I have about half the pad left on all fours and have 150,000 miles on the car and drive daily in rush hour traffic in the Washington, DC area. Maybe that is the issue. It does feel as if the automatic adjusters aren't snugging the pads close enough to the rotors. I'll have to give your suggestion a try. --Nate  

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Just bought an '04 tdi and noticed the same thing. Pedal travels far but brakes perform very well. Used to it now. Will try the parking brake adjust as I do not believe they require further bedding.  

rexdriver85

I also was having this problem with my 04. Half the pedal travel was dead space until the brakes would finally catch. I got used to it, but in a panic stop situation it can be really scary, because of the good second or two before you're brakes start applying. I bought a motive power bleeder and yesterday did a full flush with OEM brake fluid starting with the farthest caliper away from the master cylinder and working my way front. To be honest I got no bubbles or anything, just kept going until I had fresh fluid from each caliper. Took for a test drive and it was a world of difference. Brakes start applying as soon as you touch the pedal just like it should be. My car is only at 64k, as compared to you're 150k. You could have other things going on. VW's are notorious for wearing rear brakes twice as fast as fronts though, especially B5 passats. And, also notorious for rotting/rusting out e-brake cables too.  

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Brake pedal excessive travel

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Read some of the threads re above. Brakes have been bled thoroughly following the procedure here on the forum. But still same problem. Is there any way to check for problems with master cylinder and or the servo ? Thanks in anticipation Kenny  

You have pressure bled the system with a diagnostic system in basic settings mode?  

I'm using an aftermarket pressure bleeder but don't have VW diagnostic software and bleeding system. Would you recommend getting this done. ?  

It is impossible to get the system air free without being able to run basic settings.  

Okay thanks will have to get done and I will get back to the forum with the outcome Kenny  

How many times do o through the cycle of ABS bleeding ie, does the program tell you when you have completed the front brake lines and to move to the rear brake lines. Kenny  

On the older Mk20 system it was a 17 step process but on the Mk60 it is open ended so we do three. We also go around the car triggering the basic settings for each wheel and then bleed again but that could be me being obsessive, I am sort of prone to that.  

Thanks Crasher for your reply Sorry but what do you mean by a three step process Excuse my ignorance but VW methods are new to me. Kenny  

We have only ever done this with VCDS so I cannot speak for other systems. Taking your car as an example with the later Mk60 pump (2009/10 we’re very unreliable) you need the following. 1) Car off the floor on all four corners with the wheels off 2) The battery on charge with a good sized charger as the pump takes a lot of current 3) VCDS or similar which allows basic settings 4) A large brake fluid bottle and hose, preferably two 5) A pressure brake bleeder with 1 Bar regulated delivery with a couple of litres fluid 6) An assistant 7) 11mm brake bleed nipple socket or 11mm ring spanner Firstly, we go around all four callipers and let the pressure bleeder run a 1/4 litre per caliper each and at the same time in address 03, output test 3 lets the ABS pump run whilstthe person in the car presses the pedal down and back up ten times. The output test will probably time out and you may need to exit address 04, cycle the ignition, renter 03 and carry on. Then select BasicSettings 04 where VCDS gives you a menu and you select bleeding. You follow the on screen instructions which tells you to hold down the pedal and keep it firmly pressed and after a few seconds the pedal will come back at you with such force that to fight it lifts your bum out the seat but if you don’t fight it, there may be damage, never tried it! The the screen will tell you to shout to your assistant “open” and then press the pedal 10 times and hold the another click makes the pump run for a few seconds and then shout ”close”. You can do this as many times as you like, we do it three times. After this we the operate all four corners in output tests which runs the pump, locks the individual calliper it says and then opens the circuit even though you have pressed the pedal and then locks the calliper. Then you should conduct a road test in a safe place where the brakes can be applied hard enough to trigger the ABS. If you haven’t done the output tests this can bring back excess pedal travel and it is back to bleeding again! I supposed I should do video of how we do it and put it on You Tube but I hate the sound of my own voice and people who show themselves in videos tend to be narcissistic. I think I have covered everything, ask questions if not.  

Crasher said: I think I have covered everything, ask questions if not. Click to expand...

Crasher thanks for the reply, I've got VCDS set up so will follow your instructions. I think a you tube video would be a great idea, you could get an assistant to do the voice over!  

You could also ask why it is only ATE design pumps that need this when the almost identical looking Bosch design doesn’t?  

With VCDS it comes up in the display exactly what to do.  

Okay, just to make sure I have understood you when doing the output test on ABS when it says press pedal, pump the pedal 10 times. I've done the ABS module through basic settings where it says press pedal 10 times in the instructions etc. Have never done it through output test. I have checked a version VW workshop manual for the braking bleeding procedure but nothing there about bleeding ABS. Thanks once again for your patience. Kenny  

We only do the pressure bleed output tests because I think it helps, it isn't official.  

Okay Thanks will reply when done  

Okay quick update, Abs pump bled and further bleeding of system with power bleeder and a noticeable improvement with brakes but still not perfect.  

Do it again  

I was planning to, from ABS pump to double bleed of rear brakes followed by each corner using power bleeder.  

• Could it be air entering the system?
• Brakes not properly bled as I doubt they did this bleeding procedure with the software as previous post suggested?
• Caliper pins not sliding?
• but on the other hand when the brakes are working, they bite pretty sharply.
• Master cylinder problem?
• but then the brake fluid should be again low or I am missing something?
• I tested it with the engine off - 3 times pump the pedal - engine on - it sinks - engine off - 3 times pump the pedal - it becomes stiff pedal

Thanks. This is what I was thinking as well. I thought for a second again this morning that the brakes bite pretty well when the pedal is working, the fluid reservoir is full therefore no leaks, the disk and breaks pads have some life in them(logic confirmed by the bite). When the brakes are not working the pedal sinks half way, the car starts to stop and I need to press again the pedal for the brakes to fully engage therefore it must be something related to air or master cylinder or calipers issue. Will start with the basic settings pressure bleed. Thanks again.  

I will book a brake fluid change with VAG specialist as they don't seem to offer basic settings pressure bleed. They said there is no need to do this, they are pressure bleeding with software only if they change an abs pump. They will do a brake fluid change with the pressure machine without attaching any VCDS software or running the basic settings pressure bleed. Do you think this is correct?  

If air has somehow got into the ABS pump then you could run a 205 Litre drum of fluid through there and not get the air out, it is a peculiarity of ATE Mk20 onwards pumps.  

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Excessive Brake Pedal Travel

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My 1941 Chevy's brakes work fine, I just have too much free travel before the brakes start working. It's a power brake system with front disc's and back drums. The proportioning valve is on the frame well below the MC and booster. The pedal travel has been like this since I bought the car 3 years ago. I have replaced the brake fluid, bled the system, and adjusted the rear brakes with very little improvement. I recently taped 3 small nuts together and put them into the MC where the booster rod would go. It brought the pedal up but also applied the brakes so I took them out. Did I just prove that the brake pedal rod is too short? I looked at my brake pedal rod to see if it's adjustable, it doesn't seem to be unless the adjustable part is on the other side of the firewall and into the booster. Can I buy a longer brake rod? Do I have to lengthen the current brake rod? Any help would be greatly appreciated. Russ  

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Sounds to me like your pedal travel is too long (under dash stop adjustment), or the pedal swing geometry is wrong, and the rod too long lifting the pedal to that high position. Do you need all that travel? I've seen brake pedals (hanging) with multiple holes to mount the push-rod to that would lower the pedal. On some GM power booster to MC plunger, there are different length push-rods as well, two sizes I'm aware of, that would effect plunger depth, too short and it doesn't push enough fluid, too long it bottoms out in the MC.  

68NovaSS said: Sounds to me like your pedal travel is too long (under dash stop adjustment), or the pedal swing geometry is wrong, and the rod too long lifting the pedal to that high position. Do you need all that travel? I've seen brake pedals (hanging) with multiple holes to mount the push-rod to that would lower the pedal. On some GM power booster to MC plunger, there are different length push-rods as well, two sizes I'm aware of, that would effect plunger depth, too short and it doesn't push enough fluid, too long it bottoms out in the MC. Click to expand...

If the travel is really "free", i.e. the pedal/rod assembly does not contact the piston until the pedal is depressed some distance, then there are a couple choices: • Lengthen the push rod. • Adjust/modify the pedal stop. • Usually a power MC piston will have a shallow push rod hole, or will use a spacer to make it that way. So be sure the MC itself and the MC piston's push rod hole is compatible w/the pushrod you're using. If there IS contact w/the piston after just a little pedal movement, yet it still takes a lot of travel to get the brakes to engage, the master cylinder bore may be too small or the calipers/wheel cylinders too large or the pedal ratio is too high. Try the lower hole first (if you have one, that is).  

Another thread reminded me- is the MC on the firewall or below the level of the calipers, or ?  

cobalt327 said: Another thread reminded me- is the MC on the firewall or below the level of the calipers, or ? Click to expand...

Another thought, I came up against when putting all discs on my Nova, in the late '80's, some manufacturers came up with what they called a Quick Takeup MC, designed to work with brake systems where the pads didn't make full time contact with the rotor, they had a longer stroke to take up the slack before apply. It was to help with mileage requirements, cut drag. Any chance you have one?  

If three nuts were too much, how about trying two? Or one? That might tell you how much to lengthen the rod.  

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