Clutch pedal sticking when hot on track

[Inrevinc]

I started to experience a sticky clutch pedal issue with the car on the track, only happens at the end of the track day (last 2 sessions). Starts once the car is warm after 2-3 laps in those sessions and gets progressively worse.

- I come into corner and brake/downshift.
- Gear engages fine, clutch pedal comes slighlty up above friction point but won't pop all the way back up.
- Will not do it when accelerating.
- So far I've done 32 track days with my car, this issue has only happened the last 4 days. It has happened to various degrees. Each time I've had the brakes and clutch bled hoping it wouldn't happen the next time. Complete flush of brake fluid done too.
- Used gulf 1000 and Super Blue and no change in behavior.
- Brake pedal is still firm, now that the car is cool the clutch works fine.

My guess is a bad slave or master cylinder. The problem is I can't reproduce it on the street and both dealer and indy shop tell me they find nothing wrong with hydraulics.

Any way I can reproduce it or test it so that I find out what it is?

[tonythetarga]

Sounds like you're losing pressure in the slave cylinder when it heats up from track use. How many miles on the car? have you checked for leaks as well? Could be a bad hose that goes to the slave cylinder. Might be time to put a new hose and slave cylinder in, especially if the bleed didn't do anything to help.

[Inrevinc]

A small puddle appears after running the car and letting it sit. Definitely clutch/brake fluid. Car has 56,000km (35k miles). Now the dealer will have to be blind to miss it!

[Inrevinc]

Fixed at dealership, slave cylinder was to blame. Now car drives flawlessly.