General Question (mAC) Pressure Plate Failure

[Edward R. Wendell IV]

Mine worked just fine for about 80k miles except for the fact that my 
left leg was about and inch diameter larger than the right due the 
workout it was getting. The general wisdom seems to be that the pedal 
gets stiffer as the disc wears and the angle on the diaphragm spring 
fingers changes the mechanical advantage at the throwout bearing. Until 
I got the opportunity to drive another 5kcstq I thought it was supposed 
to be that way. Then one day "bang", pedal goes to floor and horrible 
racket issues forth from the bell housing. I nursed it back home by 
starting in gear etc.

The analysis after disassembly was that one of the mounting ears 
snapped off the throwout bearing. I'm still not sure why the clutch was 
so stiff as the disk didn't seem to be excessively worn i.e. I wasn't 
down to the rivets yet, but I have yet to acquire a new clutch for 
comparison. It was a Sachs clutch, most likely a replacement from what 
little info I got from the previous owner. The hydraulic system had 
been replaced as well, otherwise the extra pressure would probably have 
caused a blowout long before the thowout bearing gave up. Also, from 
what I read, had I had an 87 or later car with the aluminum clutch 
pedal instead of the earlier steel one it would have snapped in two at 
some point as well. I have a suspicion that when the clutch was 
replaced by the previous owner the friction surface was machined down 
without doing the same to the clutch mounting surface. Doing so would 
have the same effect on the leverage as having a worn disk. I have yet 
to take any measurements to verify this however.

Roy Wendell
Clarksburg WV USA
86, 87 5kcstq
87 MR2 times 2
Three turbos, two quattros, too much fun