Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
I was able to replace just the piston on my '96 without replacing entire master cylinder. I'd check out the cylinder first. It may be the rubber on the piston just deterioted or hardened over the years.
In my case I had brake fluid crystalized. I cleaned it up and polished it lightly with fine steel wool. I put the new piston in and have't had any problems.
Check Beemer Boneyard for the parts, I've found them quite a bit cheaper and they are new OEM.
Good Luck!