Steve Dallas

This. I have oodles of track hours on my OE clutch and 42K total miles, and my release bearing is just starting to talk to me. The disc and pressure plate are probably just fine. My next clutch with be Exedy OE with an upgraded release bearing.

bean137

I experienced the same issue, but was able to solve 95% of it. For people who find issues in the future, here is what I did. I think the issues are not the clutch, but a mix of old and aged parts along with a system that is difficult to bleed.

1. Replace the hydraulic system.
You will be well suited to replace the entire hydraulic system; clutch master, clutch slave, and the soft line. When I initially installed the new clutch at anything above 7,000 rpm the pedal would go instantly to the floor and stay there like it was not even connected to anything. I replaced the master first and that made it so it would at least shift. The pedal was still soft and the shift was very slow. I then replaced the slave and the soft line. That resulted in more improvement. I replaced the system with basic replacement parts; the master was Exedy and the the slave was a Beck/Arnley. Most of our cars are around 15 years old. The increase spring pressure from the pressure plate is likely more than the old, worn parts on these cars can handle and I think is where most people encounter issues. The cut off seal in the now very worn master cylinder can't cope with the line pressure and leaks back into the reservoir - that's why people post they don't see any leaks. It's an internal leak.

2. Bleeding the system.
Bleeding the system is a pain. Initially when I replaced the clutch, I didn't break any connection on the hydraulic system. I simply removed the slave so I didn't introduce any air. When I replaced the master I bled the system with the backyard standard of having a buddy pump the pedal and say "up, down..." You know how it goes. Doing this only removes a small portion of the air. If you look at the hard line coming from the master, it is routed up and above even the reservoir. It's really, really hard to get all the air out of a system with that type of routing. I used a vacuum bleeder to try and get the rest out. It was a combination of bleeding it while pulling a vacuum, having a friend either pump or hold the clutch pedal down, and running a lot of fluid through the system. That got it to be about 95%.

3. Reroute the lines.
I have not done it yet, but a fix to get the last 5% would be to reroute the hard line coming out of the master to go down below the reservoir and maybe install an bleed fitting between the line and the master itself.

I cannot explain the RPM relation to the soft pedal. My best guess is it is harmonics/vibration related. At higher RPM the vibrations disrupt the seal between the cylinder wall and the seals in the master or slave. My other suspicion is the pressure plate is borrowed from a different application and might not be balanced to the RPM a rotary engine operates at, and that is where the harmonics come from. I have no evidence of this and Exedy couldn't answer it either. Just a hunch based on the issue, and that the stage 1 clutch is a few hundred dollars cheaper than the OE spec replacement.

Hope that helps. Happy revving!