Troubleshooting C5 Clutch Hydraulics Issues
 

I have a 2001 Z06 that I've now owned for a few months. The car has around 155k miles and I really have no way of knowing what all has been replaced in the drivetrain over the years. I'm now experiencing that all too common issue with the clutch pedal sticking to the floor during quick shifts. I have tried the old turkey baster in the master cylinder reservoir flush trick a few times, but it didn't seem to do much good really. The clutch itself seems to still have good grab in it and as long as I drive the car normally, there are no issues. I got some ATE Super Blue fluid and a remote bleeder for the system. I just found out however, that in order to get to the bleeder valve, I will have to drop the whole exhaust and more. I really wish I had known this a few months ago when we had the whole exhaust off the car swapping in the long tubes and mid pipe.

All this being said, it seems the only way to solve my issues is to get under there. Bleeding the system and putting in the high performance fluid is a given, but is there anything else I should look for or replace while I'm in there? I really don't want to replace the entire clutch if this one is still good, but what about the slave or the master? The problem seems to be getting worse as of late too and I don't want to start damaging crucial drivetrain components because of improper clutch engagement.

Put in a remote slave bleeder valve. That way you can replace all the clutch fluid in a few minutes. Changing it via the reservoir method can take 20 to 30 times and then not even get it all. It still may not be your problem.

This is a common problem with these cars and there are many solutions.
- some even work
- but rarely for everyone

The clutch system does not get all that hot, so hi temp brake fluid is not necessary. The problem is that clutch dust is very fine and gets sucked past the seals and gums up the system. That's why the universal recommendation is a bleeder line.

Hello, as you have 155K on your car, my assumption here is that the clutch pedal spring may be original to your car and maybe broken OR weak.

The first step for troubleshooting a Pedal Stays on Floor (Clutch Disengaged) issue is to Inspect the clutch pedal for a loose or worn clutch pedal spring.

You may want to get an eyeball on this spring to see if it is broken and if it is not broken, you may want to consider replacing this spring as it may be weak.

If after replacing this spring and the peddle sticks to the floor, you will have to go deeper into the clutch system for more inspections.

Just search the CF/Web for the Corvette C5 Clutch Spring and you will get info on location and replacement info.

Reference info below.

PIP3821B: Removal Of The Clutch Over Center Spring - keywords cylinder hydraulic master pedal - (Apr 15, 2008)

Subject: Removal of the Clutch Over Center Spring

Models: 1997-2004 Chevrolet C5 Corvette

2005-2008 Chevrolet C6 Corvette

Equipped with a Manual Transmission

This PI was superseded to update model years and tac notes. Please discard PIP3821A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:

It appears that some Corvette owners are removing or disconnecting the clutch over center spring on their vehicles.
This is not a recommended practice and customers should be advised of the implications of such an action.
Recommendation/Instructions:

The clutch master cylinder has a compensation port that is positioned within 1 MM of the top of the stroke. The compensation port allows internal pressure in the clutch hydraulic system to be exhausted into the master cylinder and also provides for system refill as the clutch disc wears.
One purpose of the over center spring is to return the clutch pedal to the very top of the stroke to expose the compensation port. The second purpose of the spring is to provide for the designed clutch pedal feel.
Removing or disconnecting the spring may allow the clutch pedal to hang in an at rest position with the piston short of the compensation port. If the internal pressure is not exhausted the CSC may get stroked too far and a clutch hydraulic system failure may result. The C5 clutch hydraulic systems were built by AP. The C6 systems were manufactured by FTE. Also, the pedal must be in the full up position, with the compensation port exposed, to bleed properly.
Anytime a dealer gets a hydraulic system complaint, the tech should inspect to insure that the spring is in place and properly connected. Related customer complaints might include poor shift performance, improper clutch release or transmission synchronizer damage.


#PI00206: Service VME - Clutch Pedal Does Not Return When Depressed - (Jul 11, 2002)

Subject: Service VME -- Clutch Pedal Does Not Return When Depressed

Models: .

Following diagnosis might be helpful if the vehicle exhibits the described symptoms.
SERVICE VME

This is a service VME regarding 1997 through 2002 Corvettes. We’ve had several complaints of the clutch pedal not returning when depressed. If air gets into the hydraulic clutch system, the clutch pedal may not return when depressed. This may occur at low speeds, when stopped or possibly during high RPM shifts. One source of this condition may be the clutch slave cylinder. If the clutch pressure plate was not evenly torqued to the flywheel it may have been distorted. This could result in the clutch release fingers being uneven causing the clutch slave cylinder to wobble. This wobble will eventually damage the internal seal and the slave cylinder allowing air to enter the system. If this situation is present the recommended repair is to replace both the clutch slave and clutch master cylinders. A visual inspection of the pressure plate release fingers for wobble, which would appear similar to a bent wheel, should be performed when servicing the slave cylinder. If the release fingers are found to have this condition, it will also be necessary to replace the clutch assembly. Evenly torquing the pressure plate to the flywheel is necessary to prevent this condition.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
Cheers,
Goose

I'm definitely gonna try the clutch assist spring, thanks! That is a way cheaper and easier place to start. I don't see any leaks in the system so let me try that and wish me luck.

Good info 69, copied that to file.

I ordered the clutch assist spring and finally got it in yesterday. I took the car out and beat on it a little and so far, clutch is working as it should and not sticking to the floor like it was. I don't want to jump ahead and say this fixed it 100%, but it certainly does seem to be working properly now.

As the pedal starts to come up, I can now feel a sort of dual catch point that I didn't notice before just before half way to the top. This must be the master cylinder being directed to properly seal by the spring. I see why some may not like that odd feeling and remove it, but the ones that aren't experiencing any issues probably aren't still running the stock MC, for the most part at least.

A big thanks to 69. If this didn't fix it 100%, it was certainly a MAJOR improvement and flushing the MC regularly may be all I have to do for a while. I couldn't hardly drive the car before this so it was a must for sure.

Well I was thinking that spring had fixed it and it certainly helped, but last night I took it out and was doing some quick shifting and it was sticking once again. Seems to do it worse when it's really cold. Could that be something to do with the hydraulic seals?

Try taking the 2 plastic filler covers off on both sides of the bellhousing. It might be too late for anything to help your clutch but it's free to try this.

I don't think the clutch itself is shot, just the hydraulics. Clutch still feels ok. In order to remove these plastic covers you are talking about, does that mean I have to pull the whole mid pip and remove the tunnel brave just to get to it?

The turkey baster only removes contaminated fluid from the reservoir.
What you need to do is removed the caked up clutch dust that has accumulated past the actual reservoir.
The firs thing you need to is protect all the areas around the cylinder including the fender. then suck out all the fluid. then wipe out any residue with a clean cloth.
then fill with clean fluid
now you need to fashion a syringe or turkey baster with a 1/16 vacuum hose connected to it. so the connection is air tight.( be innovative. ) make the hose about 8 inches long.
now suck up some clean fluid and be careful that is does not drip.
put the 1/16 hose into the little hole at the bottom of the reservoir and feed it in as far as you can. ( about 4 to 6 inches.) with a full syringe. flush the system and you will see built up black contaminants emerging from the hole and into the clear fluid in the reservoir. based on the size of the syringe or turkey baster. several flushes will do before, you suck out the reservoir and again and wiping out the reservoir. now fill again with clean fluid. Fill the 1/16 syringe again and flush twice. Suck out the fluid and clean the reservoir. By the third time you flush the system you should see very little or no black coming out of the hole. if the black is still coming out , do it another time. it usually only takes 2 or 3 times at the most. a quart of fluid is all you need. make sure its new from a sealed container. its the packed clutch dust in the system that cause all the problems but it does flush out easily. If you do it right it should only take 1/2 hour once you have a proper syringe and hose. You should do this at least once a year. No need for a remote bleeder.. many members have added a remote bleeder only to have it leak. If the bleeder is not compromised, its a good thing to have.

They aren't that big an they are at the sides of the bellhousing towards the bottom so you should be able to get them off without removing anything. Drivers side anyway. Passenger side is behind the starter so you will have to remove the starter but it should come out with the exhaust in place. Others have reported pulling these covers has helped allow the stock clutch to survive even with a cam and head upgrade. It just lets the dust out and clean cool air in.

Best would be to pull it apart so you can both take off those covers and bleed the system to remove the old fluid in the slave cylinder.

If you're on a stock clutch the self-adjusting pressure plates are known to cause this. Might look into that if you end up ruling out the fluid. Good luck!

I would try a new OEM master. My 35k mile master was almost entirely full of black goo/tar like substance. It gets trapped in the master and no flushing will get it out. There not to expensive. My buddys 04 CTS v was having the same problem on a new clutch. The original master had 75k on it.

Also installing a remote bleeder requires dropping the trq tube.

Too bad it's wrong. The clutch assist spring has nothing to do with the sticking pedal syndrome. Far as that goes; it doesn't have that much affect on the effort needed to depress the pedal. E.T. has the most useful info above.

:iagree:

Same problem here, was fixed with a new MC. :flag:

I have 20,000 Private message help requests over the last 13 years here, The flush method I have promoted, does in fact work, people including myself, with more than 90 K on their car have successfully corrected this effect with a proper flush.. once you clean the reservoir and fill with clean fluid and insert the 1/16 hose, the amount of black contaminants that are flushed out are amazing. It works so well that the second you force fresh fluid under pressure in there it just blows out the crud... much like a power washer. Of the dozen or so people including my self who have done this, it was 100% effect for every person. It cost you 1/2 hour of your time and a quart of fresh fluid.

I failed to read Ur method for flushing the master. Deff sounds promising. Wish I knew about it 4 years ago. Lol

I did the flush method you mentioned above pretty much exactly as you described it. Did it 3 or 4 times til it was all clear, but it didn't really fix the issue.

Seems like there is more going on than the simple flush can cure. Its funny because it seems like it does this more if I take it out and start driving it hard immediately. If I take it out and drive it smooth and give it time to cycle the fluid around, it seems to be ok. I found a good deal on a Tick MC so I went ahead and got it. Not sure when I will put it in though cause that's a pretty big job. I

'm gonna play around with some of your ideas over the next few weeks and see if it helps. What if I do the pump flush with some better fluid, like ATE Blue. I have some of that now, but someone told me not to mix that in unless I doing a full bleed off flush.

IM sorry that this fix did not work for you, its the first time that Ive heard it not working unless there is a bad seal in the master causing the fluid to bypass the seal. in that case. A new unit is the only fix.