Completely Different Clutch Issue

[lalessi1]

Have a very unusual problem with my clutch... Background: I have an FE with a toploader 4 speed, 12" diaphragm clutch (LuK), Tilton hydraulic throw out bearing and Tilton master cylinder. The clearance between the retracted throw out bearing and the clutch fingers is about .060", Tilton would like to see about twice that much.

Everything works great, clutch pedal is light. engagement is smooth, no slippage. BUT as the car gets up to temperature the clutch effort gets dramatically heavier, manageable, BUT WTF? It only gets back to "normal" after the engine COMPLETELY cools down (like overnight).

[Tom S]

That's a really strange issue. I'd be pretty hard pressed to ever install a hydraulic throw out bearing. Seems like that just makes something more complicated than it needs to be but I do understand the reasons people use them. I'd worry about leaks. Standard mechanical throw out bearings do last a very long time.
Now you have to pull the trans just to adjust it & maybe fix the problem.
I tried to come up with some reasons that might explain why that is happening but I'm pretty sure that the physics of hydraulics would not support any of them.
Right now You only have 1/2 of the minimum clearance required so maybe an adjustment will fix it. Or maybe you just got a bad unit.
I wonder if or how much the clearance between the throw out bearing and the clutch fingers decrease as the fluid warms & expands? Still don't see how that would cause this weird problem.
Good luck & keep us posted!

[Tom S]

Lynn, when you pull the trans  here's something that you might consider trying in order to isolate the problem before reinstalling the trans. Pull the pressure plate, set it face down in a drill press over some same size spacers under where the pressure plate bolts to the flywheel. Rig something to put into the drill chuck to  press against the fingers & get a feel for what force it takes. Don't press those fingers very far and ruin the thing!
Then heat the pressure plate up real good with a heat gun & press it again to see if there is any real difference. Again - don't press those fingers very far and ruin the thing!
I know this might sound crazy or a waste of time but it wouldn't be much work. If anything I would expect that it would take a little less force when that pressure plate is hot but if it had some odd defect that causes some internal binding in the plate when it's hot it might save you a lot more work.

[lalessi1]

Thanks Tom for the suggestions. I kinda ran out of ideas nothing I could come up with made sense and I didn't want to pull the transmission just to stare at it. I got a couple of other suggestions and I have an inquiry into the clutch manufacturer to see if a defect of some kind in the pressure plate could cause the issue. I am also planning on talking to Tilton again. I have a couple of extra block plates to increase the clearance by spacing the bellhousing back a bit. I also bought a deeper bellhousing just in case. (That would require a custom pilot shaft bushing I think.)

[KULTULZ]

BUT as the car gets up to temperature the clutch effort gets dramatically heavier, manageable,

Is either the MC or line(s) close to an exhaust system heat source?