As you know there has been problems with both the C5 and C6 including the C6 Z06 where at certain conditions high RPM shifting and clutch pedal will not return to the "off clutch" position.

Due to some "gods" in cyberspace have as we mentioned on other posts about this make wild claims that the whole problem is due to dirty brake fluid and if you clean it often the problem will never occur.

We have always thought those makeing such claims should stick with playing with toy cars.

If any thought was used it is clear that dirty brake fluid cannot hold back the total force of the arms of the pressure plate and in fact changing the fluid often only causes brake fluid to break down due to water in the air.

So all the below is on the slave that has been in out 1999 C5 for 7 years.

Compounding the whole problem is

1. slave design, as seen you can see all the packing (grease) that was in bearing gets heated and pushed out of bearing causing bearing then to have slop movement and the packing to gum up the shaft bearing slides onto.

2. the bearing female shaft slides over the male shaft of base of slave.

3. if you look closely you see flat grooves inside of bearing shaft, there is too much free play and with the packing grease gumming up the make shaft the groove of bearing wear grooves into the male shaft and due to all the slop freeplay the bearing gets cocked and jammed onto male shaft.

4. Notice the heavy wear marks on male shaft, it is easy then for bearing to get coked on an angle and rather then slide back down shaft is jammed, metal to metal.

5. Hose from clutch pedal, notice that even after 7 years with a ton of racing that the fitting at end of hose going into slave is still clean and the hole inside of slave to clutch hose is also clean, no dirt at all.

Add centrifugal force, due to GM making a weak design so those who otherwise could not drive a clutched Corvette could.
At certain high RPMs and due to centrifugal force the arms of pressure plate have less force and with a cocked throwout bearing cannot push bearing back which then would push the fluid back to allow clutch pedal to return to its upper limit.

Once you clearly see how the inside of bearing has lost the bearing packing, how it grooves the slave shaft and the packing grease gumming up and due to freeplay it is easy to see how bearing could get jammed and not return to proper position and dirty brake fluid in no way could cause any of this.

Review the thread as to our findings as to the clutch master design failures at :
Master design failure

More images of slave/bearing

Here is the plunger seal that brake fluid would be covering and we see after all these years and being fluid had never been replaced is still clean. If fluid as being said was dirty and clogging system then seal also would be dirty.

Also look like due to force, metal ring that sits on top of seal had snapped

Hydraulic Clutch Description

The clutch hydraulic system consists of a master cylinder and an actuator cylinder.
When pressure is applied to the clutch pedal, pedal depressed, the pushrod contacts the plunger and pushes it down the bore of the master cylinder.
In the first 0.8 mm (0.031 in) of movement, the compensation port seal closes the port to the fluid reservoir tank, and as the plunger continues to move down the bore of the cylinder, the fluid is forced through the outlet line to the actuator cylinder mounted to the driveline support assembly.

As fluid is pushed down the pipe from the master cylinder, this in turn forces the piston in the actuator cylinder outward. As the actuator cylinder piston moves forward, it forces the release bearing to disengage the clutch pressure plate from the clutch disc.

On the return stroke, pedal released, the plunger moves back as a result of the return pressure of the clutch.

Fluid returns to the master cylinder and the final movement of the plunger opens the port to the fluid reservoir, allowing an unrestricted flow of fluid between system and reservoir.

More images with the worn grooves painted red to better show how bearing is not sliding freely alone the stem of slave base and how bearing can be forced on a angle a jam onto stem

On examining slave more what we find is the stem of release bearing is made of plastic.
On the bottom of it is a thin metal end cap that prevents the inner grooves ends from hitting slave stem and also prevents bearing stem from tilting.
This end cap broke, fell off and now lays at the bottom where seal to fluid in base is.
This then causes bearing to tilt, jam against slave base so it cannot move smoothly and then grind grooves into that base stem.

Thanks for the tips! I'll tear into mine and see if I can identify any other problems.

It would be interesting if you still had orginal master and test if to see if in fact it was the cause last time of the condition was solved but not the cause.

Also if you end up having to rip the drivetrain out to take pictures of the slave and also if your car had one of the bad lot of flywheels that cause pressure plate damage.

Review the TSB on this

TSB

Yep, I found the old one in the garage. I'll try to test it in the A.M. to see if it was bad at all.

Do you have any tips on testing the old one? I guess I can hold the quick connect open and see if it will push out any fluid?

GM has nothing about test of master.

I assume if master has fluid and if you push in the seal/stop at end of hose while pushing in the pedal rod fluid should pour out.

Other direction if using a air compressor push in hose end so that seal/stop open that air being pushed in should cause pedal arm then to move outward

I would make sure the clutch return spring on pedal did not break or pop off.

I looked at the original one taken out in 2006 and it is bad. You can move the clutch pedal rod in and out without opening the spring loaded fitting, the new one will not budge. This means it is not building any pressure.

Or when the hose was taken apart that seal/stop did not close all the way ?
Or when taken off and all fluid was taken out it needs to be bleed again ?
If you take the rod off the pedal with present master does it also have no pressure ?

The one that is in it now also has no pressure with the pedal removed. I can easily press it in with my hands.

The original still has fluid in it, since it is a closed system I never removed the fluid.

Once I remove the quick connect I will be able to remove the one in it. I just had to come in from the heat for a break.

I wonder if forcing the pedal up when the slave is stuck would cause the cylinder to fail?

Take the old one and check at the bottom and see if the O ring and bleeder is OK
Maybe valve comes apart and you can find what is wrong with old one and fix it and then know went wrong with the master that has been in last couple of years

Will do. I just finished replacing it and the new one operates fine.

I first tried to bleed the old one with no luck. I then took all of the hoses apart and the plunger appeared to be cocked sideways. After fixing that and bleeding, it seems to be working.

I'll box up the untouched replacement and send it.

The one I tore apart had the fluid changed within a few days of failing. So I completely agree that changing the fluid is definitely not the cure.

BTW be careful when removing the spring loaded quick connect fitting. I was lucky to find all of the pieces when it went flying across the garage.

Good work Brett,

When I get your other bad one I will see if it also has the same and if if so why ?

At least you know how to correct the problem rather then having to spend another $100 for the 4th master.

I suspect release bearing had jammed, up and down on pedal but since bearing could not return back the fluid in the slave could not push the fluid back into the master and caused some issue to be found later as plunger is a unuseable state.

Yes without a doubt the condition of brake fluid does not cause this problem where pedal never returns and when it problem occurs but then corrects itself.

I'll do images and writeup once I get your's and fully analyze it.

At this point we now have a cure for the problem you had and how to correct it without buying another master.

Is it possible that the self adjusting mechanism of the clutch causes problems that people assume are due to damaged hydraulics or old fluid?

From time to time my clutch pedal felt really strange: while pushing and also releasing it. The clutch was releasing fine, just the pedal movement was slowed down by something.

I pressure bleeded the system several times without results, replaced the master and the slave but the problem was still there.

All of a sudden, after a spirited trip on our mountais the problem desappeared. The only thing I know that changes automatically is the position of the ring inside of the pressure plate that adjusts the clutch for wear.

I can imagine that if the spring fingers arent in the correct position the whole system isn't working properly.

The brake fluid is falsely blamed from trannie not shifting to engine performance. It is the biggest myth that exists and to this day people are half ass changing part of the fluid and thinking they are preventing problems

This thread proves as issues to the Corvette design that there is both slave and master issues that have zero to do with brake fluid.

The self adjuster would effect if cutch is slipping but it would not cause the other problems to master and slave.

I assume of one of the 3 adjusters was stuck then disc would not have even clamping but that would again not effect slave functioning.

If for any reason the disc got overheated and slipped like if low speed and then spinning the tires then it might take some time for disc to get cleaned off and grap properly again.

The design of slave is different with your Camaro as the vette due to the trannie in ass end and the drivetube

I agree if the arms of pressure plate were faulty that uneven pressure would be put on throwout bearing and effect if it cocks on a angle and does not slide correctly

GM has had to post another TSB due to people getting sucked into opening the cluch fluid tank causing the brake fluid to get contaminated with water

07-07-31-001A: Clutch Hydraulic System - New Service/Owner Maintenance Information - (Sep 11, 2008)


Subject: Clutch Hydraulic System -- New Service/Owner Maintenance Information


Models: 2005-2009 Chevrolet Corvette (Including Z06 and ZR1) with Tremec 6-Speed Manual Transmission (RPOs MM6, MZ6, MH3)

This bulletin is being revised to update the models to 2009. Please discard Corporate Bulletin Number 07-07-31-001 (Section 07 -- Transmission).

This bulletin is being issued to provide dealers with additional information on servicing the clutch hydraulic system.

Please also advise customers of this new maintenance information.

Some cases have been found where the vehicle's clutch hydraulic system was contaminated with water.
Higher than expected levels of water in the clutch fluid greater than 2% may cause the clutch fluid to boil.
The presence of water in the fluid lowers the boiling point significantly; when this occurs, the driver may lose customary clutch pedal feel and performance.

To eliminate the opportunity for moisture to enter the clutch hydraulic system:

• The clutch fluid level inspection should be a VISUAL inspection only. Look through the transparent reservoir and observe the fluid level.

Avoid removing the cap !

DO NOT remove the cap just to top-off clutch fluid. Leave the system closed and sealed.

During PDI inspection or routine service, the cap should not be opened for just an inspection.

• Open containers of DOT 4 clutch fluid have a two week shelf life.
DO NOT use fluid if the container opening date is unknown or older than two weeks. DO NOT mix or re-use old fluid. Current service information already covers the issue of reuse.

• To provide the best clutch operation, it is recommended that the owner change the clutch fluid every two years.

Please flush and replace with P/N 88958860 (P/N 88901244 in Canada) or equivalent DOT 4.