After rebuilding my master cylinder (and adding stainless lines) a little while ago, I have recently developed a problem with fluid leaking out from under the master cylinder cap. This appears to be associated with the vibrations produced by high RPMS -- at 7,000 it is practically streaming out from under the cap. This happens regardless of how hard I screw down the cap.
I am going to order a new rubber diaphragm, since my current one has some tiny cracks, but I would be surprised if this is the cause. Is it possible that I am putting the cap on wrong? I always fill to the fill line, then place the black diaphragm on top, then screw on the cap tightly. Any help or past experience is appreciated!!