Low (temporarily) clutch pedal

[Mike Litherous]

Hey chaps.

Often when I rev out my car hard close to te redline often the clutch pedal on the gear change doesn't bounce back to its original position resting about 1/2 to 1/3 closer to the flywheel than original. After another gear change or 2 not in anger it restores back to original spot.

Hydraulics?

Or something more sinister at play perhaps?

Anyone else experiance this phenomenon?

Thanks in advance.

 

[NU13]

Hey chaps.

Often when I rev out my car hard close to te redline often the clutch pedal on the gear change doesn't bounce back to its original position resting about 1/2 to 1/3 closer to the flywheel than original. After another gear change or 2 not in anger it restores back to original spot.

Hydraulics?

Or something more sinister at play perhaps?

Anyone else experiance this phenomenon?

Thanks in advance.

Do you have aftermarket extractors?

It's a well know issue through out the GM performance range with manual transmissions. I'm no expert but i'll try and explain. I'm having the same issue with my VE GTS. Whats happening is two things. 1, the stock slave cylender has a very small orific for the clutch fluid to get through...this isn't the main reason for the issue but it certainly doesn't help. So when you want clutch fluid transferring quickly it is being choked at this point. One sollution is to pull the slave out and drill this choke point out to be a little bigger. 2, issue is that the clutch fluid line passes close to the extractors and when you/me gets excited and gives it a bit the extractors obviously heat up (a lot hotter than the stock extractors) and this over heats the clutch fluid and produces a gas in the clutch fluid line thus reducing the effectiveness of the fluid. I've been reading up on this and there are actually many makes, not just GM, such as the 350Z that suffers from this problem. One of the fixes that work for many people is to wrap the clutch fluid line in some sort of heat resistant material (even over bake tin foil works aparently). I've ordered some proper heat resistant wrap and metal zip ties off Flebay. I'll be wrapping my clutch line and also rigging up the wrap to cover the reservoir as well.
So basically nothing to be overly worried about. But one sure fire fix is a new aftermarket clutch.
Hope this helps.

 

[NU13]

For instance here is a Viper owner with over heated clutch fluid issues

Header Wrap to keep Clutch Fluid from Boiling [PIC]

 

[ducker85]

I was about to say slave cylinder. I needa get mine changed. Im at the point now where one flatshift and its on the floor. I think there's a few other bits but the slave cylinder is number one thing to do first. Make sure you regularly check and change your fluid too as it goes black quick!!

 

[Mike Litherous]

Thanks guys for the logical explanations. Yes I have extractors and it being only temporary this makes sense. I'll heat wrap the clutch line. The fluidly hasn't been changed since I had the car (nearly 3 yr) so it may be worth flushing it out and replacing it with some good quality high temp dot 4.1 even dot 5.1 so it's boiling off threshold is a little higher.

Thanks again.

 

[NU13]

Yes change the clutch fluid, it's well over due and i'll be putting in a high temp fluid myself as well. I keep seeing people with our problem recommending Castrol SRF. Very expensive but very good apparently.

 

[Mike Litherous]

I've just ordered a thermotech heat shield.

On the castrol SRF it absorbs moisture really easily. I've used it in my track car but went back to motul dot 5.1 as it's better at resisting moisture and is a lot less pricey.

Abit of a side issue is on the track car I installed some titanium plates between the brake pads and the pistons. This helped keep the pedal consistent as the brembos have aluminuim pistons which transfer heat to the fluid too easily.

Thanks again for the responces. Much appreciated.

 

[sidecar55]

Make sure the system is flushed properly as SRF is synthetic based & will react with mineral fluid. It makes a horrible mess inside cylinders & will cause problems.
I run SRF in my roadrace sidecar & there nothing better.

 

[NU13]

I've just ordered a thermotech heat shield.

On the castrol SRF it absorbs moisture really easily. I've used it in my track car but went back to motul dot 5.1 as it's better at resisting moisture and is a lot less pricey.

Abit of a side issue is on the track car I installed some titanium plates between the brake pads and the pistons. This helped keep the pedal consistent as the brembos have aluminuim pistons which transfer heat to the fluid too easily.

Thanks again for the responces. Much appreciated.

Thanks for info, i'll stay away from the SRF then and go for the 5.1 Motul.

 

[Mike Litherous]

Make sure the system is flushed properly as SRF is synthetic based & will react with mineral fluid. It makes a horrible mess inside cylinders & will cause problems.
I run SRF in my roadrace sidecar & there nothing better.

I found the SRF very good also. Just expensive for an occasional road going track day car. The Motul 5.1 was pretty good also for my purposes and significantly less.

Mate you must have some balls to do sidecar racing.