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#2626 - 06/18/08 12:45 PM Brake fluid cause of jammed clutch debunked  
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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

Attached Files 99pressure.jpg99release.jpgrelease.jpgslave.jpgslave2.jpg

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#2627 - 06/18/08 12:47 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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More images of slave/bearing

Attached Files slave3.jpgslave4.jpgslave6.jpgslave7.jpgslave8.jpg

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#2628 - 06/18/08 01:50 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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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

Attached Files slave9.jpg

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#2643 - 06/23/08 08:38 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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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.


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#2701 - 07/17/08 06:37 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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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

Attached Files slave1.jpgslave2.jpgslave3.jpg

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#2703 - 07/18/08 02:48 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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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.

Attached Files s2stem.jpgs1break.jpgs3stem.jpgs4tilt.jpgs5spring.jpg

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#2704 - 07/18/08 03:05 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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Thanks for the tips! I'll tear into mine and see if I can identify any other problems.


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#2705 - 07/18/08 06:12 PM Re: Brake fluid cause of jammed clutch debunked [Re: Brett Hunter]  
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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


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#2706 - 07/18/08 07:16 PM Re: Brake fluid cause of jammed clutch debunked [Re: teamzr1]  
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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?


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#2707 - 07/18/08 08:12 PM Re: Brake fluid cause of jammed clutch debunked [Re: Brett Hunter]  
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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.


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