Symptoms of a bad ABS module

[xtmsports]

Hey guys, I have pressure bled my brakes many many many times thanks to all you kind gentlemen's advice, but it still seems to have air in the system.

Brakes will work fine for awile, then all of sudden, work like crap and feel like air got in them and start grinding and the back brakes start to squeal, probably from the front brake grabbing too much or the rear brakes not grabbing enough because of air.

I've gone completely mad with this problem. the only other thing I can thik of that could be bad is the ABS module since i have changed everythng else out except for the brake hoses and the ABS module.


What would be the typical symptoms of a bad ABS module?

Thanks fellas!

[632 Regal]

grinding, squeeling, what did you do? I mean did you replace brakes? rotors? both? might be something stupid but with more information at least I can give you an educated smart ass remark, without that I can only be a smart ass.

Hope you follow me here.

[shogun]

check here, maybe helps, from my website
http://www.bba-reman.com/bmwabsfaults.htm

[xtmsports]

grinding, squeeling, what did you do? I mean did you replace brakes? rotors? both? might be something stupid but with more information at least I can give you an educated smart ass remark, without that I can only be a smart ass.

Hope you follow me here.

hahaha, that's funny.
Well I have replaced almost everything, pad, rotors,calipers, master cylinder.

I pressure bleed the brakes and all seems "okay" still doesnt feel like smooth braking. But as i drive and use the brakes more, it seems almost to bottom out and i can feel the pads grinding up front and the rear brakes start to squeak..

Later on in the day, everything is fine, then eventually it starts grinding and squealing again.

Yesterday, I had to hit the brakes hard to avoid hitting a car in front of me, that scared the hell out of me because when i hit the brakes, it didnt stop the car, almost as if the pads couldnt get a tight grip and lost grip and gripped again..luckily it stopped in time though. It felt like air in the lines causing the calipers to not operating in unisom.

I've worked with brakes before but never had this kinda of special BMW brake problem. Already spent about $600 on parts, and I am hesitant on giving up and taking it to a dealer and paying another $500 or whatever.

[zygoteer]

Generation of 'noises' takes energy - in this case braking energy ... this means that the source of the problem is most likely to be mechanical, it just 'might' be the ABS valving & control but I seriously doubt it (if it was you would have felt the pressure variations on the pedal).

From the effects you describe, I would re-check and check again the installation of ALL the parts ... my guess (and it is a guess of course) is that something is not properly fitted - caliper/pad positioning is the first thing I would check.

Sorry to hear about your 'brown trouser' moment with no brakes, but ask yourself : is avoiding a nasty unpredictable accident worth $500 ?
... I bet after such an incident you would say yes.