andy530i

I'm having some intermittent issues with the brake pedal on my 530i. First of all I noticed that lately the pedal feels hard when I go to start the engine; almost like I pumped the brakes while the car was off. The next thing is when slowing to a stop appying constant pressure everything is fine, but if I let off then apply pressure again sometimes the pedal goes to the floor! I'm at 49K right now brakes and rotors were replaced around 45k almost a year ago with none of these issues until a couple of days ago. BMW warranty is out.

Am I looking at a MC problem or do I have air in my lines somehow?

525iEnjoy

If it feels like a low pedal and you know for a fact your pads and rotors are within spec, then yes air could be in the lines. When was your brake fluid changed last @ the dealer?

andy530i

Yes, the brake fluid was changed by the dealer November 09.

andy530i

My SA seems to think the brake booster is going out due to the heat?? They have seen a couple fail in the last few weeks. Any thoughts on this?

acuteperformance

Your brake booster is broken.

525iEnjoy

What year and make where the models that failed? I wouldnt think a 04-06 530i would just fail all of a sudden. If the bladder on the hydro part failed then you would have a soft pedal all the time and hopefully a brake light would come on for that. Makes sense

When you brake, does the pedal grab high middle or low? Cause mid to low or low brake pedal travel will give you the symptoms of worn pads/rotors or air in the system. In my car I found that both rear calipers had ZERO fluid come out of them, then my ABS wasnt engaging, and I had mid/low pedal before grabbing. I did 3 full cycles of bleeding and got all that air out. So it can be you just need a really good brake bleeding.


When you drive pay attention to how much travel you have in your pedal. It should be around 1 inch-ish you'll notice if you go any further

andy530i

The brakes feel normal to me except for the situation I described which only happens on occasion. I initially thought I'd see a brake light too if the booster was out, but the booster is operated by vaccum, and to my knowledge doesn't have any electronics or not related to fluid level. I'm going to test the check valve and the vaccum line for proper operation/ leaks tonight. I'm totally with you though, how could that system fail at 49k? I've never heard of such a thing.

I'll let you know what I find out tonight if I have a chance to do a few tests.

andy530i

Check valve was fine and the vacuum line was fine too. I disconnected the vacuum line and had a buddy push the brake as far as he could then plugged the hole where the vacuum line connects then released the pedal... it didn't hold so I'm assuming that if this is the correct test method for identifying a faulty booster then it is indeed bad. If that's not the right way to test it, someone let me know please.

Thanks

545iBMW

Had the same issue.
BMWNA wouldn't recall this as it will cost them tons of money.

I suggest you do the same thing as I did.
Report it to NHTSA here:

http://www.safercar.gov/

click Defects and Recalls
then click File a Complaint

I filed mine last month and got a call today.
This hopefully will push BMW to recall this issue.

Check my thread regarding this.

andy530i

I filed the complaint, so maybe one day there will be a recall. I hope they refund the cost of having this repaired if they do decide to recall.