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Hey everyone, I have a 2003 bmw 530i (M package). I was driving the car about a week ago and as I was driving I noticed that the brake pedal progressively began to get more firm, I also noticed the car was slowing down without me touching the breaks. Gradually, the car came to a halt in the road when the breaks overpowered the throttle. (it appears as though it may be only one or both of the rear wheels) after coming to a stop, the: brake, ABS, and traction lights all came on the cluster. Unsure of what to do, I turned off the car and let it sit. after a few hours, went back to the car and it was completely fine (no lights). Today, (after about 200 miles or so) the car did the same thing. I did the same thing, (let the car sit) and it was perfectly fine. Does anyone have any idea what the problem could be? Getting kind of sketched out driving this car now. :eek:
 

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Under the lift arms
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yeah dont drive it..

there are few options

you have a cailber that is locking up (2nd )

you have a bad master cylinder (first)

you have a bad brake booster (3rd)


when it happens... you need to identify by putting your hand by your brakes if they are screaming hot
then you need to id if the check valve in the suckjet is function (you can remove vacuum from the booster manually ) *this might speed up your "after a few hours"



Its unlikely that a single corner will be able to stop a car.. even a whole axle locked up..

More then likely its all 4 corners ....

NOT to mention if it was 1 side of 1 axle.. they should be screaming hot... smoke'n brake pads


My bet is on the master or the booster (there are other known problems like boosters with frozen water in them) Im sure some people who have had brake problems like this will chime in
 

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As mentioned it has to be at least 2 wheels. If one corner or the other was locking the car would want to go one way or the other. If it is the rear It could be the ABS or Traction control. IF you drive agian before you figure it out try driving w/ the traction control off.
 
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