Please help! I have a carbon black E39 M5 2003 model, which has a strange problem with its brakes. When i am travelling at moderate speeds in town traffic and i have to 'feather' the brakes when traffic either slows or comes to a halt in front i have experienced the brake pedal going right down to the carpet! The car is low mileage, well looked after and in pristine condition and owned by me from new. I have had the car into my local BMW dealer countless times but they can find nothing wrong. The pads are fine, the brake fluid has been replaced and bled numerous times but the problem persists. The dealer has even spoken to BMW 'M' in Germany who say this is impossible - but i know because i have experienced it!!!
has anyone else experienced this problem, or has anyone any ideas???
i must mention that under normal/hard usage the brakes are fine.
I have heard of some similiar issues with M5s before. After a long battle, a full replacement of the brake system lines with a proper bleeding seemed to clear things up. Hope this helps.
I had this on my '01 when it was delivered. I had it once before years ago on another car, and fixed it myself, so I know how it happens.
The problem is a hairline scratch inside the brake master cylinder running lengthwise inside the cylinder, probably from debris when it was made. When you hit the brakes hard, the rubber sliding seal on the piston comes under a lot of pressure and it compresses and squeezes into the scratch and plugs the leak. If you just lightly press the pedal, the rubber doesn't get squeezed into the scratch, and so it doesn't plug the leak and fluid gets around the piston and the pedal sinks gracefully to the floor.
In the old days, you'd just take it apart and hone the master cylinder. Nowadays, they just put in a new one. In any case your dealer will rule the car off the road until it's fixed (mine did), but the good news is that the rest of the braking system is and will continue to be fine.
I had this on my '01 when it was delivered. I had it once before years ago on another car, and fixed it myself, so I know how it happens.
The problem is a hairline scratch inside the brake master cylinder running lengthwise inside the cylinder, probably from debris when it was made. When you hit the brakes hard, the rubber sliding seal on the piston comes under a lot of pressure and it compresses and squeezes into the scratch and plugs the leak. If you just lightly press the pedal, the rubber doesn't get squeezed into the scratch, and so it doesn't plug the leak and fluid gets around the piston and the pedal sinks gracefully to the floor.
In the old days, you'd just take it apart and hone the master cylinder. Nowadays, they just put in a new one. In any case your dealer will rule the car off the road until it's fixed (mine did), but the good news is that the rest of the braking system is and will continue to be fine. - Thanks JJ, i will pass on your info to my local BMW dealer.
E39 M5 brake problems
Re: E39 M5 brake problems
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