Finally got back to Laguna Seca after having my TOB retaining clip unwind itself on track last time I was there. I since installed an ACT Monoblock reusing the mystery clutch, pressure plate, and light-ish flywheel on the car. I had previously installed a braided clutch line and pulled the delay valve. Fluid was good (ATE 200) and the clutch engaged very nicely mid pedal stroke.

Fast forward to last weekend where I’m going down the front straight, shifting from 3-4, and the clutch pedal goes to the floor… Instantly I’m thinking the clip let go again so I pull off-line and get a hand out the window, eventually tugging the trannny into fourth. As I make my way off track the pedal starts to get a little body. In nursing the car back to the pits I have to come to a stop -> shut down the engine. To go again I select 1st, clutch down and hit the starter thinking it’s just going to crawl away on the starter motor (not engine). Well it seems the slave is doing a little something and the clutch slips like crazy – smoke/dust pours out the hood scoop. Within a sec it’s clamped and we’re off.

Back in the pits I bleed the slave getting some moderately dark fluid out, no air though. The clutch pedal now feels normal again so I take it out for a test. Dragging the brakes I can go full power in 1st without the clutch slipping, shifting feels fine. About 10 min into the next session the pedal starts to feel a little soft again so I come in, pack the car, and drive four hours home at a pretty decent pace on twisty roads without incident.

Once home I went through Jack's clutch pedal adjustment procedure and found that I was a little off max adjustment, maybe three threads. The car would creep a bit at the 5600 launch limiter. Now the clutch actuates just off the top of the pedal stroke. This all just has to do with the clutch not disengaging though and shouldn't have any affect on my situation.

Has anyone experienced loss of clutch pedal like this?


More background:
I shift typically 8 times per sub 2min lap at Lugna,
No I don’t ride the clutch pedal,
I have a really high degree of mechanical empathy and shift / clutch gently,
Temps were in the 60-70’s, no other thermal issues with the car,
The car’s making right around 300/300 at the wheels.

Pictures of the clutch package are here:
https://www.evolutionm.net/forums/me...rank-9511.html

 

Do you have a leak?

 

Not that I know of. Everything appears to be clean and tidy.

 

So the clutch fluid is the same as the Brake fluid are you sure you didn't boil the brake fluid and it caused the clutch issue.

 

the brake and clutch share the same reservoir but if you boil the brake fluid, it happens in the calipers, not the reservoir.

the seals on your clutch master or slave cylinder is probably on it's way out. i've never heard of anyone boiling fluid in the clutch.

 

You'll never boil clutch fluid. It's not connected to anything that gets hot. As what Honda guy said, something isn't working right, be it slave/master or something's up with the clutch itself.

 

That's pretty much my thought too at this point. The clutch still feels fine driving around on the street, albeit at a much higher engagement point now that I've adjusted it per Jacks video. I'll order a slave rebuild kit and replace the seals. They're the only ones even in a sorta kinda warm neighborhood.

If it was an issue with the clutch itself I'd not have pedal problems, it'd be slipping or making noise or some other failure mode.

 

not always true. ive seen many different issues with clutches such as binding on the trans input shaft. this can cause the pedal to stick to the floor cause the pressure plate wont return back to rest position (and the car will act like its stuck in gear)

 

(p.s. that was me, above. todd was logged into the shop computer and i didnt realize it)

 

+1. I had a number of hydraulic issues at the track last year but not to the extent of yours. My braided line vibrated 45* at the banjo fitting on the slave and was grinding against the trans. The car was 100% drivable but the pedal wouldn't hold pressure for long if I held the pedal down. I later found a very small hole in the line and when moved off the trans, it dumped nearly all the fluid in just a short 5 minute drive and lost complete function.

Before finding that I thought it may have been either slave or master cylinder.

Inspect the line just to be sure.