C4 hydraulic clutch

[Ernest C.]

We have a 1984 with a 4plus3 transmission the we purchased new. The car now has only 10600 miles and am having trouble shifting. The clutch reservoir is full but it seems when I press the clutch pedal in it does not engage the clutch enough to avoid grinding into reverse or low. When moving because the gears are synchronized if I'm very careful it shifts ok.I don't know whether there are adjustments for the clutch.
Any ideas or help would be appreciated.
Thank you

[Joe L.]

Re: C4 hydraulic clutch

We have a 1984 with a 4plus3 transmission the we purchased new. The car now has only 10600 miles and am having trouble shifting. The clutch reservoir is full but it seems when I press the clutch pedal in it does not engage the clutch enough to avoid grinding into reverse or low. When moving because the gears are synchronized if I'm very careful it shifts ok.I don't know whether there are adjustments for the clutch.
Any ideas or help would be appreciated.
Thank you

Ernest-----


There is no adjustment on these C4 hydraulic clutches. If the clutch actuation system is, indeed, malfunctioning, then you probably need a new clutch master or slave cylinder.

[Jim T.]

Re: C4 hydraulic clutch

Not a Corvette, but another car I drove for years had a hydraulic clutch. Best thing I ever did was rebuild it and use silicone brake fluid.
With regular brake fluid, it would turn black from the rubber parts in the master and slave.
When my 96 LT4's system requires replacement I may try silicone brake fluid in it as well since I have had such good results with it. No problems yet after 13 years and 41K miles. Not a lot of shifting though with 96% of miles on interstates and highways.

[Terry M.]

Re: C4 hydraulic clutch

Contamination of the clutch fluid is a BIG issue with the C6s. There is even a sticky thread about it in the C6 Z06 forum on Corvette Forum. Scientific analysis of the clutch fluid reveals the discoloration is from clutch dust. It must get past the seals somehow, and it rapidly contaminates the fluid. A regular regimen of clutch fluid changes is the solution. Chevrolet now recommends clutch fluid change every 2 years for the new C6s -- I think that started with 2009 cars. My 2008 Owner's Manual doesn't mention changing clutch fluid.

http://forums.corvetteforum.com/c6-z06-discussion/2250372-clutch-pedal-issues-how-to-prevent-and-cure.html

I will have the tools and some fluid with me on the Road Tour -- we can have a REAL tech session along the way.

You might consider changing the clutch fluid and see if it helps. Use DOT 4 fluid.

[Joe L.]

Re: C4 hydraulic clutch

Contamination of the clutch fluid is a BIG issue with the C6s. There is even a sticky thread about it in the C6 Z06 forum on Corvette Forum. Scientific analysis of the clutch fluid reveals the discoloration is from clutch dust. It must get past the seals somehow, and it rapidly contaminates the fluid. A regular regimen of clutch fluid changes is the solution. Chevrolet now recommends clutch fluid change every 2 years for the new C6s -- I think that started with 2009 cars. My 2008 Owner's Manual doesn't mention changing clutch fluid.

http://forums.corvetteforum.com/c6-z06-discussion/2250372-clutch-pedal-issues-how-to-prevent-and-cure.html

I will have the tools and some fluid with me on the Road Tour -- we can have a REAL tech session along the way.

You might consider changing the clutch fluid and see if it helps. Use DOT 4 fluid.

Terry-----


GM specifies a special hydraulic fluid for hydraulic clutch systems. It's GM #12345347.

[Terry M.]

Re: C4 hydraulic clutch

I quickly looked through my receipts, but couldn't find the part number for the clutch fluid. Thanks for posting it. It is in my owner's manual too, but that was not close at hand either. It is called "Super DOT 4 Clutch and Brake Fluid" about $8 for a pint. It is the only brake fluid I have seen that comes in a metal can -- but I am sure there are others -- it is not a common packaging method, although it should be.

If one reads the thread I linked to -- that individual has found Prestone DOT 4 brake fluid to do a serviceable job, and it is easier to find than the GM fluid. It is interesting that for C6 production (and probably other years as well) Chevrolet has used DOT3 for brake fluid and DOT 4 for clutch fluid. That makes it sound like the more severs use is in the clutch.

[Clem Z.]

Re: C4 hydraulic clutch

Contamination of the clutch fluid is a BIG issue with the C6s. There is even a sticky thread about it in the C6 Z06 forum on Corvette Forum. Scientific analysis of the clutch fluid reveals the discoloration is from clutch dust. It must get past the seals somehow, and it rapidly contaminates the fluid. A regular regimen of clutch fluid changes is the solution. Chevrolet now recommends clutch fluid change every 2 years for the new C6s -- I think that started with 2009 cars. My 2008 Owner's Manual doesn't mention changing clutch fluid.

http://forums.corvetteforum.com/c6-z06-discussion/2250372-clutch-pedal-issues-how-to-prevent-and-cure.html

I will have the tools and some fluid with me on the Road Tour -- we can have a REAL tech session along the way.

You might consider changing the clutch fluid and see if it helps. Use DOT 4 fluid.

i think most of this problem is with the guys who "power shift",never backing off of the gas pedal and cause a lot of clutch dust to be generated which get into the slave cylinder. i am not a C-4 guy but i though the clutch slave cylinder was external.

[Terry M.]

Re: C4 hydraulic clutch

Clem,
I don't know about C4 clutch either, but the C6 is internal. The slave is like the throwout bearing, and expands in that position. Even with vents in the bellhousing the clutch area gets real hot on my Z06. The Cat convertors beign right there is no help either.

[Clem Z.]

Re: C4 hydraulic clutch

Clem,
I don't know about C4 clutch either, but the C6 is internal. The slave is like the throwout bearing, and expands in that position. Even with vents in the bellhousing the clutch area gets real hot on my Z06. The Cat convertors beign right there is no help either.

i know the C-5 and up are internal but i think the C-4 are external bolted to the side of the bell housing,but i never owned a C-4 so this is from memory which ain't be so good lately

[Ernest C.]

Re: C4 hydraulic clutch

Thanks for the suggestions. I'm taking it back to the Chev dealer with a copy of these threads.
Thanks again

[Terry M.]

Re: C4 hydraulic clutch

No knowledge of C4s here either -- but if it is external a good flush and bleed ought to be a no-brainer.

[William C.]

Re: C4 hydraulic clutch

C-4 slave is indeed external, at least through '91, slave bolts directly onto the bellhousing.

[Terry M.]

Re: C4 hydraulic clutch

Now that I think about it, I recall Dr. Mike (#14) posting about bleeding the C4 slave cylinder. The bleed screw is on the bottom of the slave (great for access, but sucks for function), and he had to unbolt the slave and rotate it to get the bleed screw to the top so the air would come out. I would guess his issue was on an LT4, so that would make it likely 1990 and newer.

[Joe L.]

Re: C4 hydraulic clutch

Now that I think about it, I recall Dr. Mike (#14) posting about bleeding the C4 slave cylinder. The bleed screw is on the bottom of the slave (great for access, but sucks for function), and he had to unbolt the slave and rotate it to get the bleed screw to the top so the air would come out. I would guess his issue was on an LT4, so that would make it likely 1990 and newer.

Terry-----


All C4's, 1984 through 1996, use an external clutch slave cylinder. However, the slave cylinder is not the same for all C4's. I do think that the bleeder valve is on the bottom of all of them, though. The service manual specifies that the cylinder must be bled with it disconnected and the bleeder valve rotated to the top. It's a VERY difficult and frustrating operation.

[John M.]

Re: C4 hydraulic clutch

It's a VERY difficult and frustrating operation.

Like many on the C4...