I have a 328i e90 with braking issues. Okay as I was getting off the freeway I was braking pretty hard then I turned off the dsc to "drift" a little since it was raining. Right after that my brake pedal stiffened up, so I have to apply tons of pressure to get the vehicle to stop. No lights are on as I have read on some threads that a faulty abs typically turns on brake, abs, and dsc lights. Not sure it may be the abs pump and not the abs 'computer'? Just changed the brake pads and had cleaned the calipers before the incident. It's not the brake booster because I did the test, stiff before and after turning on the car. I'm going to bleed the brake line to see if that does it. Any info would be great, thanks in advance!
It IS the brake booster, or the vacuum line to the brake booster, or the vacuum pump.
A failed ABS pump will cause lots of warning lights, but it will NOT cause a stiff brake pedal - that's a boost failure.
The "test" you mentioned of the booster, if you described it correctly, is not a valid test. I'd recommend checking the vacuum hose to the brake booster, from one end to the other.
Chris Powell
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Yea the "test" I mentioned was pumping the brake pedal while the car is off, then while still pressing the brake pedal it should sink once i turned on car. the pedal is stiff at all times
Okay so the end of the vacuum hose connected to the booster has very minimal suctioning, does that mean the booster is the culprit.
thanks again for your input
Last edited by lowkey.e90; 12-08-2018 at 03:44 PM.
With the engine running, that line should have excellent vacuum. Make really sure the line isn't broken or the seal isn't leaking, or the vacuum isn't going away somewhere else. I really haven't experienced many issues with this pump, although I've heard they can give trouble.
If you don't have good vacuum on this line, you won't have boost.
EDIT: I seem to recall having dealt with a split rubber hose at the pump before....check the entire line.
Last edited by bmwdirtracer; 12-08-2018 at 10:57 PM.
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
Have you recently had the PCV recall done? Check the vacuum line to the booster. There's a snap together connection right above the alternator that is disconnected to do the recall work. If it's snapped properly, check the end of it where it snaps onto the vacuum pump.
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