my friend has a clutch problem on his 86 951.

he has a KEP stg 1 pp, a 930 disc and stock flywheel.

the problem is the pp won't seperate and free the disc.

we changed the fork and the slave cylinder first. the fork has full travel in the inspection window. when looking through the hole for the starter I can see the pp move maybe 1-2 mm but it doesn't free the disc. I slid the tt to the bellhousing and when he presses the clutch I can't spin the tt shaft.

can the pp itself go bad? I inspected it and it looked fine, nothing seemed broken cracked or out place. the surface looked even and smooth. the disc looked practically new.

the throwout bearing had a little bit of play, but I don't know how that could be it.

any thoughts on what the problem could be?

 

im going with the crack on the pressure plate :L)

 

I have a recent clutch and have a taste of this problem. Until it gets warmed up, the disc sticks to the flywheel or PP, enough to make shifting heavy, not enough to actually drag the engine. I'm thinking it is either the grease on the splines of the disc is too thick (thins out when warm), the splines are too tight, or the disc is catching on the rim of the flywheel (OD of the disc too large). I could not get all the shims on the release bearing to save my life, I also wonder if that limits the amount the PP withdraws.

When a diaphragm spring cracks, you have no pressure at all, it just flops around, the clutch will massively slip.

 

Can you see through the inspection hole is the fork is cracked? You say it moves all the way, but then say the PP doesn't move? Maybe the tips of the fork have broken off or something? I know ST had an issue to that extent when he was using a KEP PP on his car.