[A.F.]

Hello all,
I have a 2017 330i and I'm having some issues with my brakes. There is about 1-2 inches of dead travel in the brake pedal where there is 0 engagement, and then past that, the brake pedal works fine. There are no leaks in the brake system, and the brake pads all still have decent life left.

Some background information about the issue, a few months ago I had my brake booster go bad, brake fluid was leaking into the booster and eventually caused it to start leaking and I had to have it replaced. The shop recommended replacing the master cylinder as well. I ordered all genuine parts except for the master cylinder because that was on backorder at the time, so I ordered my master cylinder from Rockauto (Raybestos), and the mechanic replaced everything. Now my original issue was resolved, but this left me with the issue I mentioned above about the dead travel in the brake pedal. The mechanic tried bleeding the brakes multiple times, and I even had another shop bleed the brakes and they still feel the same.

Does anyone have any ideas about what I should do from here? At this point, I've been driving like this for the past 2,000 miles and it hasn't gotten any better or worse, but it is very annoying.

[cfm56d7b]

Welcome!

First - how many miles does you car have? Are you an original owner?

1-2 inches of dead travel after all the work being done means the problem still exists. Are the shops you mentioned BMW-centric shops or "we do everything made by everyone" shops?

The likely root causes:

1. Despite the prior bleeding procedures, air remains present in the brake system.

2. Corrosion of brake lines. Brake line can leak. Are the brake lines still original? When the brake fluid was being replaced, an experienced shop would recommend replace the brake lines either with OEM or aftermarket stainless steel ones.

3. Leaks around the caliper piston seal.

4. Brake booster and/or master cylinder are defective. It happens.

5. Air bubbles can be trapped in ABS module. Shops which have ISTA tool will flush the brakes properly.

ABS system has many other components which require specialized expertise to diagnose.

Is there a BMW-centric shop in your area?

[A.F.]

Thank you for getting back to me. So the car only has about 78,000 miles on it. And it’s always been a west coast car so no rust or anything like that. I’m not the original owner, I’m the second owner of the car but I’ve had it for a while now.

The shops were not BMW certified shops. The brake lines are all original still, both shops inspected all the lines and verified that there were no leaks. And when I took my car to bmw this week for an oil change, the service technicians noticed the issue and inspected the brake lines and everything for leaks also and did not find any. And the brake fluid level has remained full for the last 2,000 miles so I’m thinking it’s probably not a leak.

At this point I was thinking it’s probably either a bad master cylinder since that’s the one part that’s not genuine. But air in the ABS system could definitely be a possibility as well, although the shop mentioned they used their computer to perform the brake bleed, which activates the abs system.

[cfm56d7b]

Originally Posted by A.F.

Thank you for getting back to me. So the car only has about 78,000 miles on it. And it’s always been a west coast car so no rust or anything like that. I’m not the original owner, I’m the second owner of the car but I’ve had it for a while now.

The shops were not BMW certified shops. The brake lines are all original still, both shops inspected all the lines and verified that there were no leaks. And when I took my car to bmw this week for an oil change, the service technicians noticed the issue and inspected the brake lines and everything for leaks also and did not find any. And the brake fluid level has remained full for the last 2,000 miles so I’m thinking it’s probably not a leak.

At this point I was thinking it’s probably either a bad master cylinder since that’s the one part that’s not genuine. But air in the ABS system could definitely be a possibility as well, although the shop mentioned they used their computer to perform the brake bleed, which activates the abs system.

Got it. Thanks for the additional details.

The circle of root causes is now a bit smaller. What are your next steps? Take the vehicle to a BMW indy shop? Any issues with brakes - no matter how small - would be prudent not to ignore.

[A.F.]

Originally Posted by cfm56d7b

Got it. Thanks for the additional details.

The circle of root causes is now a bit smaller. What are your next steps? Take the vehicle to a BMW indy shop? Any issues with brakes - no matter how small - would be prudent not to ignore.

At this point, I am leaning towards ordering a genuine master cylinder, and having it replaced. I can order a genuine one for about $370ish, and then I will probably take it to a BMW indy shop for installation. It seems like the most probable cause of the issue at his point.

[cfm56d7b]

Originally Posted by A.F.

At this point, I am leaning towards ordering a genuine master cylinder, and having it replaced. I can order a genuine one for about $370ish, and then I will probably take it to a BMW indy shop for installation. It seems like the most probable cause of the issue at his point.

Makes sense. Hope the problem will be found and rectified. Please share an update later.

[alohasurftoad]

I'm almost certain it is because you have not done and need to accomplish the ISTA+ bleeding procedure.

[cfm56d7b]

Originally Posted by alohasurftoad

I'm almost certain it is because you have not done and need to accomplish the ISTA+ bleeding procedure.

alohasurftoad Thanks for joining the discussion and helping.

OP mentioned "the shop mentioned they used their computer to perform the brake bleed" but it wasn't clear if ISTA+ bleeding procedure was used.

OP, before purchasing a new master cylinder I also suggest to verify first if ISTA+ bleeding procedure was used.

[A.F.]

Thank you for the feedback. I actually don’t know if it was the ISTA+ bleeding procedure. I haven’t ordered a master cylinder yet, but that definitely may be worth looking into.
I appreciate it

[cfm56d7b]

Originally Posted by A.F.

Thank you for the feedback. I actually don’t know if it was the ISTA+ bleeding procedure. I haven’t ordered a master cylinder yet, but that definitely may be worth looking into.
I appreciate it

Please keep us updated. Very interested in learning the root cause.