[TheBrightSide]

I recently installed a brand new OEM AC Delco (FTE branded) clutch master cylinder; after the clutch pedal died on me and I replaced that as a resort to not replacing the clutch slave cylinder and other related transmission parts (complicated and expensive process).

It’s currently a super hot summer in CA here, with temps spiking well over 100+ F on the daily for the past 2 months or so. I’ve bled my clutch/clutch fluid from the bleeder valve on the slave cylinder, where it sticks out through the transmission bell housing. I also made sure that there weren’t any leaks from me installing the hard clutch line into the new CMC, as well as checking the condition of the lower clutch line at the CSC, and also the clutch fluid hose going to my separate clutch fluid reservoir.

I use high temp, racing DOT 4 brake fluid, that’s well over 500+ F in the dry boiling point. I typically swap out the fluid in the reservoir once every month or every other month, depending on how often I drive. I can see what appears to be either clutch dust particles, or some sort of other tiny debris, settling at the top of the clutch fluid reservoir; which I try to clean out when I do the clutch fluid swap.

Anyhow, my clutch pedal was fine, but I notice that when my engine bay temps spike (esp on hot days), my clutch pedal feels a little softer at the top; just not to the point of actually losing hydraulic pressure and causing “dead pedal”. I have the factory clutch return spring removed, and have rigged up my own DIY return spring (resembling that of a Lingenfelter clutch return spring); but you are still able to feel any play on the top of the clutch pedal regardless.

I sometimes take the cap off of my clutch fluid reservoir and pump the clutch pedal a handful of times, which appears to take away the very barely noticeable “softness” at the top of the clutch pedal. I figured I’d bleed again, but it would simply come as soon as temps spike, and then stay until I’d open the cap and pump the clutch pedal again.

As of today though… I do notice that pumping the pedal actually made the soft spot worse. It’s not generating any loss of pressure or dead pedal, but I think I’ll bleed it AGAIN, and then go from there. I typically pressure bleed my clutch pedal by pumping it, and then jamming a rod/stick between my seat and the pedal; then I go to crack the bleed valve loose on the CSC. This seems to work without issue.

Maybe I’m just not bleeding it enough? The “soft” spot on the very top of the clutch pedal didn’t worsen till about a month in, after I bled it properly a 3rd time. Sometimes pumping it after I put the cap back on the fluid reservoir helps, but I figured that it would typically only work with the cap OFF. I’m so confused now…..