Help, long brake pedal travel

[pawa_k2001]

I am trying to resolve the long brake pedal travel on my M3. I have bled the system multiple times, both with the 2 person system and power bleeder. I also used autologic to bleed the ABS pump. The brakes work when you step on them, ABS kicks in. The problem is that the pedal travel is longer than usual(I have another 2002 M3 to compare to). I tried to test the master cylinder by starting the car and stepping on the brakes to see if pedal goes down to the floor, pedal goes down just below the throttle pedal top, it doesn't drop any lower. The brake pedal doesn't sink slowly to its firm level, once you press on it, it goes down to a certain spot and doesn't drop lower.

What and how each system can I test to resolve this problem?

[01M3Fan]

Interested to see what you find, my brakes are similar. When I bought the car new, I remember pedal firmed up with short travel. After BMW bled brakes in one the the covered service, the travel lengthened and I foolishly didn't bring it back.

Later when working this issue I found that my ABS unit would work in the car correctly but wouldn't communicate with BMW Service computer (can't remember the initials) to go into bleed mode. So I sourced a used ABS module and solved that and then replaced the master cylinder as I suspected BMW screwed that it - better, but not like stock.

I've bled these a lot using various methods and Turner Motorsports has done them a few times and said their function is normal. I've had the car on the track a bunch and no issues - but miss that new car pedal feel.

When I next replace my rotors I'm going to try going back to OEM pads for the street to see if that helps - I've read they will help, but other than better cold bite, I struggle with how that will affect pedal travel.

Good luck!!

[SteelGreyM]

This might sound stupid but how are your pads and rotors doing? Whenever my pads are low I always have what feels like more brake travel and less pressure. Take a peek at them all.

[pawa_k2001]

I have ZCP/CSL OEM front pads with PFC V3 front in the front and ZCP/ZCP rotor with stock M3 pad in the rear. Stopping distance is no different compared to my old 2002 M3(which is now owned by my brother) but my pedal is longer. Both M3s are 2002.

[mrgizmo04]

Did you recently switch from harder compound pads? Pads make a difference in pedal feel.

Other than that, any brake fluid leaks that you notice or level in reservoir dropping slowly? Master cylinder/brake booster seals most likely culprit of softer pedal if negative on the above.

[Speed Monkey]

Your brake calipers, are they stock single piston sliders, or is your sled fitted with Brembo calipers (or similar)? If your sled does have Brembo type calipers, each caliper has multiple bleeding ports; each port must be bled, otherwise a soft brake pedal will result. Good luck in chasing down your problem.

Second Thoughts - The E46M braking system is vacuum assisted. Perhaps you have a vacuum leak in the system. I randomly looked on ECS’s website and found this... Notice the description below that ECS offers about this part; It matches your issue, BUT I’m not advocating that parts be “thrown” at your braking system; test the part before buying. Again, good luck.

[pawa_k2001]

Did you recently switch from harder compound pads? Pads make a difference in pedal feel.

Other than that, any brake fluid leaks that you notice or level in reservoir dropping slowly? Master cylinder/brake booster seals most likely culprit of softer pedal if negative on the above.

Just rebuilt my stock calipers, running OEM pads. No leaks anywhere, even looked under the boots on each caliper piston.

Your brake calipers, are they stock single piston sliders, or is your sled fitted with Brembo calipers (or similar)? If your sled does have Brembo type calipers, each caliper has multiple bleeding ports; each port must be bled, otherwise a soft brake pedal will result. Good luck in chasing down your problem.

Stock ZCP calipers.


I am at a loss of what it can be. The stopping distance is the same compared to my old M3 and ABS system works the same(kicks in when you really step on it). The only difference is how far down the pedal goes and because of that, I can't trust the brakes. Plus at the track its harder to rev-match downshift since the brake pedal goes past the throttle pedal and makes you ride the throttle if you are not careful.

[mrgizmo04]

Per Monkey's and my comment, possibly brake booster related. When you bled them with 2 people method, did you make sure not to let the pedal travel all the way to the floor?

[pawa_k2001]

Per Monkey's and my comment, possibly brake booster related. When you bled them with 2 people method, did you make sure not to let the pedal travel all the way to the floor?

What is a good way of testing a brake booster?

[COVID-19]

If you pressed the brake pedal all the way down you could of torn a seal inside the master cylinder.

[mrgizmo04]

What is a good way of testing a brake booster?

it is all based on vacuum assist so there are a lot of vacuum and fluid lines and seals.

Few tests you can follow. Watch the shorter one pretty much all the way through, the longer one, you can just watch first few mins to get the idea.

https://youtu.be/QogQ8Ip04Vk

https://youtu.be/_HFMrYUH-Ig