Clutch pedal sticks - need suggestions!

[krnlpnc]

In desperate need of advice on this one...

Issue: After a few high RPM shifts, the clutch pedal becomes firm and then sticks to the floor. If I slow down and pump the clutch pedal a few times, it returns to normal. The car has actually been in this condition for over a year and is absolutely fine on the street under normal driving conditions. But after 2 laps on a road track or a few drag races on the street, the pedal goes hard and then sticks until it cools down (which it does within 60 seconds).

Attempts to fix thus far: replaced clutch master cylinder and throw-out bearing. The clutch lines are heavily wrapped in thermal tape and I've tried SRF clutch fluid to avoid a boiling issue, however the problem remains easily reproducible.

Background: the car is only mildly modified and putting down about 370hp at the wheels. C5 Z06 clutch and aluminum flywheel have been installed for about 2 years. LG long tube headers. Car has 95,000 miles...she's no garage queen.

It's at the shop now and my mechanic is running out of ideas. He's next going to wrap the headers in thermal tape trying to isolate if it's a heat problem.

Anyone else run into this? Any suggestions are greatly appreciated!

 

[njlouc]

Back to basics - the only thing left is the fluid and the slave unit.
You may have to use hitemp fluid, or the slave is worn.

 

[krnlpnc]

Castrol SRF 500 degree fluid is being used (and flushed and filled before each track event) and the slave cylinder (throw-out bearing) has just been replaced. Still can't make it two laps around Laguna Seca...

 

[motorman]

make sure the MC is returning all the way back past the bleed hole. if you do not have a return spring that could be your problem

 

[bwing]

In desperate need of advice on this one...

Issue: After a few high RPM shifts, the clutch pedal becomes firm and then sticks to the floor. If I slow down and pump the clutch pedal a few times, it returns to normal. The car has actually been in this condition for over a year and is absolutely fine on the street under normal driving conditions. But after 2 laps on a road track or a few drag races on the street, the pedal goes hard and then sticks until it cools down (which it does within 60 seconds).

Attempts to fix thus far: replaced clutch master cylinder and throw-out bearing. The clutch lines are heavily wrapped in thermal tape and I've tried SRF clutch fluid to avoid a boiling issue, however the problem remains easily reproducible.

Background: the car is only mildly modified and putting down about 370hp at the wheels. C5 Z06 clutch and aluminum flywheel have been installed for about 2 years. LG long tube headers. Car has 95,000 miles...she's no garage queen.

It's at the shop now and my mechanic is running out of ideas. He's next going to wrap the headers in thermal tape trying to isolate if it's a heat problem.

Anyone else run into this? Any suggestions are greatly appreciated!

Check this site. It may answer your questions.

Clutch_Care

 

[Bioscache2]

Check this site. It may answer your questions.

Clutch_Care

Awesome site, I just had the car in to replace a coil that went bad on me and the tech recommended that I have the clutch fluid flushed. I agreed because I had never done it and while I don't track my car, I definitely do drive spirited and at 116k miles and never having done the clutch, I figure most fluids probably are in need of flushing. I agreed and it was expensive, 200 bucks in tech time, but now that I've read this site I will do it on my own. The tech recommended doing it every 2 years.

 

[Eddie 70]

I use the Ranger Method on my clutch fluid about once every oil change to keep this from happening. It used to happen to my car after a 30 mile ride on the interstate. I could pull off at my exit and my clutch would be really stiff from just normal driving. I hopped on the net and found Rangers webpage and have been doing the fluid change for some time now. It seems to be helping with my car as it is my daily driver. When I got my car it only had 12k miles on it and it had these symptoms. They seem to be gone now.

I have read somewhere at sometime there is an orifice that is very small to control the return of the fluid. This orifice can be increased to help some with this. If I come across this info again I will post it here.

 

[c4c5specialist]

HI there,
Facts need to be understood.

Nothing more, nothing less.

You are most likely dealing with clutch pressure plate fingers that are NOT even, and they are side loading the concentric slave at high RPMs.

Not uncommon and can be repaired by remove the clutch pressure plate and CORRECTLY installing a new one.

Allthebest, c4c5

 

[Bioscache2]

HI there,
Facts need to be understood.

Nothing more, nothing less.

You are most likely dealing with clutch pressure plate fingers that are NOT even, and they are side loading the concentric slave at high RPMs.

Not uncommon and can be repaired by remove the clutch pressure plate and CORRECTLY installing a new one.

Allthebest, c4c5

Hey c4c5 can you comment on the interval recommended for changing out the clutch fluid for a manual and whether the ranger procedure would be effective or is a flush always required? Thanks.

 

[c4c5specialist]

Hey c4c5 can you comment on the interval recommended for changing out the clutch fluid for a manual and whether the ranger procedure would be effective or is a flush always required? Thanks.

HI there,
GM factory recommendations is 2 years/24000 miles.

Second, there is NO WAY that you can effectively remove all the fluid and contamination UNLESS you completely bleed the system of all old fluid.

That is only achieved by removing the converter assemblies, tunnel plate and loosening the 11 mm bleeder screw and pumping the clutch pedal while someone underneath opens and closes the bleeder screw.

The correct way to check your clutch fluid is to NEVER EVER open the cap. Use a bright flashlight from the side of the container and the light will illuminate the fluid in the reservoir.

Allthebest, c4c5

 

[Ron222]

In desperate need of advice on this one...

Issue: After a few high RPM shifts, the clutch pedal becomes firm and then sticks to the floor. If I slow down and pump the clutch pedal a few times, it returns to normal. The car has actually been in this condition for over a year and is absolutely fine on the street under normal driving conditions. But after 2 laps on a road track or a few drag races on the street, the pedal goes hard and then sticks until it cools down (which it does within 60 seconds).

Attempts to fix thus far: replaced clutch master cylinder and throw-out bearing. The clutch lines are heavily wrapped in thermal tape and I've tried SRF clutch fluid to avoid a boiling issue, however the problem remains easily reproducible.

Background: the car is only mildly modified and putting down about 370hp at the wheels. C5 Z06 clutch and aluminum flywheel have been installed for about 2 years. LG long tube headers. Car has 95,000 miles...she's no garage queen.

It's at the shop now and my mechanic is running out of ideas. He's next going to wrap the headers in thermal tape trying to isolate if it's a heat problem.

Anyone else run into this? Any suggestions are greatly appreciated!

I'm running in to the same problem with my '04, you might want to check this out the Tick Performance Adjustable Clutch Master Cylinder Kit from Tick Performance. Here's the link.

www.tick-performance.com/tickshift/parts/c5corvette/hydraulics/#master

Quite a few folks on the forum have installed it and had real good luck with it. As a matter of fact I spoke with Geoff at Next Level Performance about it and they have had good luck with it as well. I'm installing both the Master cylinder and remote bleeder as well after the holidays...Again I've heard nothing but good stuff about this set up and, like you, this sticky clutch pedal is really getting old. Hope this helps.

 

[Gdad45]

Factory Restriction on Slave Cylinder Piston

I use the Ranger Method on my clutch fluid about once every oil change to keep this from happening. It used to happen to my car after a 30 mile ride on the interstate. I could pull off at my exit and my clutch would be really stiff from just normal driving. I hopped on the net and found Rangers webpage and have been doing the fluid change for some time now. It seems to be helping with my car as it is my daily driver. When I got my car it only had 12k miles on it and it had these symptoms. They seem to be gone now.

I have read somewhere at sometime there is an orifice that is very small to control the return of the fluid. This orifice can be increased to help some with this. If I come across this info again I will post it here.

I read an article about a new Camaro having a stuck clutch after several fast shifts. Apparently GM restricted the return fluid in the slave cylinder to make the clutch engage smoothly. The fluid hasn't bled back by the time the fast second shift occurs.