E30 Brake problem discussion from bimmerforums

[rumatt]

I found this brake question interesting. Any thoughts? This guy answers a lot of questions in the E30 forum over there and has helped me as well.

http://forums.bimmerforums.com/forum...d.php?t=362049

A master cylinder that irradically looses seal sounds odd.

At the BMW CCA SD Autocross this weekend i was giving students rides around the course and in a hard braking zone my pedal suddenly sunk halfway to the floor and i had drastically reduced braking power and went straight off the course. I pumped the brakes and the pedal came back. I had brakes for the rest of the run, then on the next run it did it twice out of about 20 braking zones per run so i parked the car. No brake fluid leaks, calipers are all dry, so i'm thinking it's a failing master cylinder. I had similar symptoms on my Golf GTi about 15 years ago and it turned out to be a bad master. The primary circuit was failing but the secondary circuit at least gave me some braking power (about 30%).

I drove the car 125 miles home and about half the time the pedal would be fine, and the other half it would sink halfway down and i had to pump em to get the pedal back. I made it home safely and parked it in the garage.

So does this sound like a failing master cylinder? It has 176,000 miles on it, the last 35K of those being hard miles compliments of me.....

[lip277]

If there are no signs of fluid leaking anywhere else-
Then it would have to be the MC.

Regardless - The MC is cheap and easy enough to replace, that I'd do it anyway with the age and driving style the fella gives the car.

I replaced the MC on the 2002 for no 'real' reason other than it was ~20 years old. While I didn't have any problems or funny pedal feel before, the new MC sure did firm things up a bit. And - for me it was cheap ($125) and easy enough to do.

[bren]

You might enjoy this thread also:
http://forums.bimmerforums.com/forum...d.php?t=362120