Boiling Clutch Fluid
 

First track day in the Z

Thunder Hill, 5 mile. They said it’s the longest track in America

Temps hit 104 by 11am, so it was a brutal day

Car was running fine until lap 8 when I lost the clutch pedal, sinking down to the floor with no pressure. I was near pit area so I was able to leave the track safely. No leak was detected, but the fluid had expanded and turned dark so everyone’s conclusion was boiled fluid. Fluid level was above max After ah hour in the paddock, I was able to get it in gear and limp home. By the next days it was drivable again

Drivetrain setup is South Bend Stage 2 Clutch and 18lb flywheel
Zspeed HD CSC (v1, I think, since it was purchased in 2015)
OEM Master cylinder
Motul RBF 600, new, swapped a few months earlier

1) I sprang for some Endless RF650, figuring it’s better not to **** around. This should be the largest part of a solution, right?

2) Also got the Z1 SS upper hardline and insulated lower clutch line. I didn’t realize I already had an insulated SS clutch line when I put in Zspeed HD CSC but that was nearly 10 years ago. I might as well swap it out for the newer Z1 line, right?

3) anything else to keep the clutch fluid temps down?

Any chance your HD CSC is dying? I’m surprised you boiled the fluid with RBF600 in it and with an insulated clutch line. How frequently are you shifting on that track? lol


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I have pretty much same clutch setup with v1 HD CSC but stage 3 along with GTM supercharger. When I used to run rbf 600, my clutch would get very soft during some NYC traffic and would get softer on hot track days. I switched to castrol SRF and never looked back. From my own experience and periodically checking the fluid using brake fluid tester, the SRF treated me much better than RBF and would last much longer before absorbed moisture.

I dropped to 2nd a couple times, and I am a novice so I have no doubt I probably shifted more than necessary

I used Castrol SRF too. :tup: