C6 clutch question

[eboch]

I'm a new C6 owner ... I'm not that familiar with the clutches in these Corvettes. I have driven enough standards to have a feeling for how a clutch ought to feel. The clutch on my 2005 does the following;

1/ the pedal doesn't return all the way to the top

2/ it feels like the clutch is engaging near the bottom of the pedal throw ... probably about 3/4 of the way down

3/ when driving around, shifting seems to work properly ... but when stationary, it can be difficult to get into gear at times (i.e. into reverse before shutdown)

4/ clutch fluid level is OK, I've tried pumping the pedal vigorously to see of there is any change to how the clutch works ... nothing.

5/ when driving the clutch does not feel like its slipping ... I have not driven "hard" though.

Anyone out there have any tips? does this seem "right"?

Is there any adjustment in the clutch system?

Thanks
eboch

 

[Patrick]

First of all, eboch, welcome to the . I'm glad you found us.

Regarding the clutch- my own personal experience stems from having a manual transmission 1990 C4, 2003 C5 Z06 and my current 2006 C6 convertible. And I can state as fact that the feel of the clutch is different in all them.

Yes, it does require a deep push of the clutch to engage it. But it's one of those ideosynchracies of any car that you learn, and then it become sort of rote memory. You don't give it a second thought after a while.

Let me ask- how long have you owned yours? And what previous vehicles with manual transmissions have you owned? Your experiences with the clutch "feel" on other cars may be instructive here.

Now, the downside is unless you're Ontario, California, you may not have much of an opportunity to really get comfortable with the clutch on your C6 until the weather changes, but your descriptions aren't sounding too much out of the ordinary.

And, above all, please feel free to post some pictures of your ride when you get a chance. The locals here love the chance to drool over pictures of new Corvettes.


-Patrick

 

[eboch]

First of all, eboch, welcome to the . I'm glad you found us.

Regarding the clutch- my own personal experience stems from having a manual transmission 1990 C4, 2003 C5 Z06 and my current 2006 C6 convertible. And I can state as fact that the feel of the clutch is different in all them.

Yes, it does require a deep push of the clutch to engage it. But it's one of those ideosynchracies of any car that you learn, and then it become sort of rote memory. You don't give it a second thought after a while.

Let me ask- how long have you owned yours? And what previous vehicles with manual transmissions have you owned? Your experiences with the clutch "feel" on other cars may be instructive here.

Now, the downside is unless you're Ontario, California, you may not have much of an opportunity to really get comfortable with the clutch on your C6 until the weather changes, but your descriptions aren't sounding too much out of the ordinary.

And, above all, please feel free to post some pictures of your ride when you get a chance. The locals here love the chance to drool over pictures of new Corvettes.


-Patrick

Thanks Patrick.

.... snow on the ground up here ... not Corvette weather.

Is it usual to be a little difficult to get into gear when stationary, engine running?

eboch

 

[Patrick]

Thanks Patrick.

.... snow on the ground up here ... not Corvette weather.

Is it usual to be a little difficult to get into gear when stationary, engine running?

eboch

Not that I've noticed. Normally, when I pull up to a light, I leave it in neutral, and I've not experienced a problem putting it into first gear when I get the green light.

It sounds like you may be finding the catch point on your clutch a little deeper than you've experienced on other manual transmissions you've driven. Give it time and a little familiarity.

Unfortunately, with snow on the ground, you may have to post-pone those moments a bit.


-Patrick

 

[eboch]

Not that I've noticed. Normally, when I pull up to a light, I leave it in neutral, and I've not experienced a problem putting it into first gear when I get the green light.

It sounds like you may be finding the catch point on your clutch a little deeper than you've experienced on other manual transmissions you've driven. Give it time and a little familiarity.

Unfortunately, with snow on the ground, you may have to post-pone those moments a bit.


-Patrick

Thanks Patrick.

.... still under warranty ... so I'm going to bring it in to the local Corvette dealer as soon as the roads are a bit dry.

Regards
eboch

 

[TODD L GRIFFITH]

My clutch used to do that after a few hot shifts. I'd take it to the dealer, or syphon off fluid from the clutch fluid reservoir and replace with new DOT 3 brake fluid a few times after driving. You will get a whole fluid exchange in short order.

 

[c4c5specialist]

Hi there,
Its sounds to me like you havent owned the car since new.
First, yes, there is a pressure plate adjustment that compensates for clutch friction disc wear.
Second, your overcenter bias spring may be broken, creating the lack of return to the complete top of the travel. That spring is CRITICAL to how your clutch operates hydraulically.
Third, any modifications to the vehicle???
4th, you should change your clutch fluid every 2 years/24000 miles, whichever comes first.
This is due to revised maintenance suggestions from GM.
The engagement should be about 1" pedal travel from the floor.
That when you should feel engagement.
Allthebest, c4c5

 

[eboch]

Thanks Todd. I was intending on a fluid change ..... since I don't really know when the last change occured. The manual suggests DOT 4 fluid though .... is there some reason you suggest DOT 3?

c4c5; you are right I have not owned the car since new ... so I'm not entirely sure I even have a problem. The clutch spring located under the dash is there and not broken.... I looked for that previously.

The clutch does engage ~ 1 - 1.5 inches off the floor ... so that sounds consistent with your comment. I still can't explain why it can be difficult to get into gear when stationary though. When its in 1st it will creep forward ever so slowly ("inching")... indicates that I'm not getting full disengagement of the driveline. These two observations are really where my questions come from....my thought was that the clutch is not quite separating.

where are the adjustments on a C6 clutch? are they on the springs (as per a C5)? Also ... does the system bleed air out by itself ... or does it have to be manually bled?

Thanks
Erik

 

[TODD L GRIFFITH]

Thanks Todd. I was intending on a fluid change ..... since I don't really know when the last change occured. The manual suggests DOT 4 fluid though .... is there some reason you suggest DOT 3?
Thanks
Erik

Use DOT 4 if that's what the manual suggests. The rest, I would trust in whatever c4c5 recommends.

 

[c4c5specialist]

HI there,
This suggests to me that you have a hydraulic issue that you are NOT getting enough throw out of the slave cylinder to completely disengage the clutch.
This would require first a bleeding of the clutch to make sure there is NO air.
Make sure your carpet is NOT bunching up under the pedal.
Make sure your clutch start switch is NOT binding, stopping the pedal before full travel is achieved.
If all of these are ok, then either the master cylinder or the slave are not working correctly.
Allthebest, c4c5

 

[eboch]

HI there,
This suggests to me that you have a hydraulic issue that you are NOT getting enough throw out of the slave cylinder to completely disengage the clutch.
This would require first a bleeding of the clutch to make sure there is NO air.
Make sure your carpet is NOT bunching up under the pedal.
Make sure your clutch start switch is NOT binding, stopping the pedal before full travel is achieved.
If all of these are ok, then either the master cylinder or the slave are not working correctly.
Allthebest, c4c5

Thanks ... I think I'm on the same page ... needs to be bled. Is there a way this can be done without taking out the exhaust and the driveshaft cover to get at the bleed valve? I took a quick look and it did not seem obviously accessible without removing these.

eboch

 

[eboch]

....the dealer says the fluid is "contaminated" ... says it does not "look" right. He says it has a funny black residue that settles out of the fluid. Therefore he suggests that the fluid is not brake fluid and therefore has damaged the hydraulics causing the black residue. As a result, the warranty on these parts has been voided. As I noted, I am a new owner of this C6 so I don't factually know what fluid was used. There is a decent amount of evidence in the cars VIS history to suggest that authorized GM dealers tended to the car and that the only clutch-related repair was a throw-out bearing replacement. I contacted this dealer and they claim that they did not touch the fluid during this repair ... and of course they claim that they would not put the wrong fluid in even if they did. It just seems like a real stretch that someone would put the wrong fluid in.... let alone a GM dealer.

Anyway, the hydraulic system was bled out to replace the fluid ... but my clutch pedal return and marginal clutch disengagement problem are still present.

I have suggested to the dealer (and GM Warranty) that there is a lot of evidence of water ingress problems causing reduced boiling points and therefore odd fluid coloring.... including a few GM TSBs that clearly show that GM is aware of a "contamination" problem ... but the rest is anecdotal .... which GM warranty people won't use to grant me a warranty repair on the hydraulics.

Does anyone have any other info on this? Anything from GM themselves that help me convince GM warrarty that that the hydraulics are simply faulty and should in fact be covered by warranty.

Thanks
eboch

 

[c4c5specialist]

....the dealer says the fluid is "contaminated" ... says it does not "look" right. He says it has a funny black residue that settles out of the fluid. Therefore he suggests that the fluid is not brake fluid and therefore has damaged the hydraulics causing the black residue. As a result, the warranty on these parts has been voided. As I noted, I am a new owner of this C6 so I don't factually know what fluid was used. There is a decent amount of evidence in the cars VIS history to suggest that authorized GM dealers tended to the car and that the only clutch-related repair was a throw-out bearing replacement. I contacted this dealer and they claim that they did not touch the fluid during this repair ... and of course they claim that they would not put the wrong fluid in even if they did. It just seems like a real stretch that someone would put the wrong fluid in.... let alone a GM dealer.

Anyway, the hydraulic system was bled out to replace the fluid ... but my clutch pedal return and marginal clutch disengagement problem are still present.

I have suggested to the dealer (and GM Warranty) that there is a lot of evidence of water ingress problems causing reduced boiling points and therefore odd fluid coloring.... including a few GM TSBs that clearly show that GM is aware of a "contamination" problem ... but the rest is anecdotal .... which GM warranty people won't use to grant me a warranty repair on the hydraulics.

Does anyone have any other info on this? Anything from GM themselves that help me convince GM warrarty that that the hydraulics are simply faulty and should in fact be covered by warranty.

Thanks
eboch

HI there,
First, they did the slave cylinder, so right there the system has to be opened.
Not a fun job, by the way.
Very simply, suggest that they check the documents as follows.
And have them print them out to show you.
First, TSB 07.07.31.001 tells them about how to check the fluid and also the possibility of contamination by opening the reservoir too much.
Next, document id 2048769 should be read.
That explains a few possibilities about the clutch pressure plate possibly self adjusting too far.
As for the contamination, all clutch fluid turns over time.
The correct part number listed should be 88901244 IN CANADA ONLY.
Get your field service manager involved, its not like fluid doesnt turn dark with time, IT DOES. It is normal. I do not believe you have a contamination issue. Have them reprint your invoices and show you the part numbers installed.
Allthebest, c4c5

 

[eboch]

Thanks for the reply C4C5.

The GM VIS doesn't say that the slave was done ... only the throw-out bearing. According to GM Warranty, the dealer work order for the throw-out work does not show that the fluid was changed at that time. Even if it did, I don't think I'd have any luck getting them to say they did anything wrong. The VIS does not show any other clutch related work.

I'll have a adialog with the dealer regarding the other docs you refer to. I think I have one of them.

.... assuming I'm not going to get any joy from GM |Warraty ... I'll therefore be tearing this down to fix it ... I thought I'd first play with it some more. Under the assumption that the old fluid left some sort of deposits in the slave that were binding it or compromising the seals, I worked the pedal ...a lot .... like 100+ times. After a while, the pedal started to return all the way to the top about 1/10 of the time. The other problem I had ....stand-still shifting into gear.... also seemed to be much better after this.

I then pulled the clutch linkage off the pedal ... the linkage itself seems to come all the way back up when not impeded by the pedal (& over-center spring). This seems to indicate that the hydraulics are trying to return. I oiled the various moving parts, including the over-center spring attachment points ... seemed to help a bit ... 1/5 times the pedal would come back up. Oddly enough, the pedal with no clutch linkage attached seems to "catch' part way up. Next, I'm going to try the set-up with the over-center spring removed ... maybe this spring is worn/faulty. More info to come.

eboch

 

[c4c5specialist]

HI there,
DO NOT REMOVE THE OVER CENTER SPRING>
There is a document within GM NOT TO REMOVE IT!!!!!! Document 1839924 in the GM database.
This creates a lack of fluid bypass within the hydraulic system. IF the spring was bad, it would be broken.
Allthebest, c4c5

 

[eboch]

Thanks c4c5;

... yes I understand that the over-center spring must not be [premanently] removed.

In order to eliminate the possibility that the pedal mechanicals are binding (and therefore inhibiting the pedal return), I'm going to do some [temporary] experiments . The a worn or binding spring may be my problem. If it is, I'll replace it ... I will not be running without one. If the pedal & spring are OK, I going to tackle the hydraulics.

Are the master and slave cylinders rebuildable in these cars....or is full replacement the only option?

eboch

 

[c4c5specialist]

HI there,
When you had the throwout bearing replaced, that is the whole unit, slave and throwout together as one assembly.
So, you should only want to do the master cylinder.
As of this writing, they are NOT rebuildable.
Allthebest, c4c5

 

[eboch]

Thanks for the continued info C4C5.

...interesting that the throw-out and slave are one assembly. Thats tells me that to do the throw-out, the hydraulics had to be dealt with which would force new fluid to be added and the system to be bled. GM Warranty is saying that this did not happen (??) .... I need to get a copy of the R.O. for this work. It shows on the VIS as "K0060 - pedal, shaft and/or bushing, clutch - replace" ... the dealer tells me that this was a throw-out replacement .... does that make sense?

Regards
eboch

 

[c4c5specialist]

Tell you what.
Do one better, send me your VIN over private messenger here.
I will do some research.
Allthebest, c4c5

 

[eboch]

Done. Thanks.

eboch