car has been sitting. on first drive clutch stuck to the floor. after i pulled it up it was fine. same happened several times. then it it started sometimes to come up, but not all the way (maybe 1-2" short), in between it was normal. now, after about 50-100 miles, its good. no problems.

im very curious what goes on mecanically/hydraulically to make the clutch act like that and then to "fix itself" (hopefully). i read a lot and talked to people, not really finding an answer, speculations ranging from spring/excenter on pedal to neccessary clutch replacement.

thoughts?

 

There is a service bulletin/recall that was issued on the C6 for the clutch master cylinder replace. Your master clutch cylinder needs to be replaced. Do a quick search on the Forum or Google and you will find all the info you need.

 

This. GM made a revised clutch master assembly. The updated part has a black reservoir; old part has a clear reservoir.

Pretty easy to replace. Remove front driver's side wheel. Remove wheel well access panel. Disconnect connecting rod from clutch pedal inside the car. Disconnect clutch line going to master; it has a clip and uses a quick disconnect that has a valve that will close when not connected. Undo two nuts/bolts securing the master. Remove and replace with the new master. Re-install everything.

The new part comes pre-filled with fluid. And the hardest part is getting the clutch lines re-connected. Needs a bit of force and is somewhat difficult to get leverage in the small space. You will know the lines are connected once they make an audible click.

I replaced mine a couple of years ago. Took about an hour.

 

This could also be the result of dirty clutch fluid and the fix may be as easy as replacing the clutch fluid. Do a search for 'Ranger method' which details the process of replacing the fluid. I would do that first. I have a 2006 Z06 with 235k miles on it and have never replaced the clutch master assembly.

 

As stated ablove, replace 'old' original MC w/ revised replacement.
This clutch pedal nonsense will not happen again.

 

I will disagree with all of the above and state that sometimes the above potential solutions do not fix a low clutch pedal or one that sticks to the floor. I tried them all with zero success on my 2008 Z06. Rangering the clutch fluid, revised clutch master assembly (black reservoir). hiring a dealer to bleed the clutch hydraulics, and the only thing that fixed mine was replacing the whole assembly with an aftermarket clutch. I will say that the only time my clutch pedal would sink partway or fully to the floor was to get the clutch really hot, which only occurred when running my car on the track. This was not caused by excessive shifting or any slippage of the clutch; it was driven by heat even with no shifting. I now have a Monster LT-1 twin clutch and the problem has never recurred.

 

Do this first. Impressive!

 

Absolutely do the "ranger method" FIRST before anything else! It is literally so easy to do AND costs almost nothing but brake fluid, a very small amount, no less.

HINT: Exchange the Clutch brake fluid YEARLY with the ranger method and MANY (not all) clutch issues will be prevented........

 

The clutch master cylinder failed on my 2006 a couple of months ago. No warning. Went to the floor.
Only 20k miles on the car.

 

All good that everyone understands the first thing to check, and the second when their clutch pedal goes to the floor. YMMBY different. Good luck.

 

thank you all. it happened when clutch was "cold", just driving around a bit, btw.

im more interested in whats exactly happening than in what to do at his point.

"dirdy" fluid: seals sticking because of that somewhere?
old master: how is the replacement different?
what in the clutch itself can make pedal not come up and then go away?
air in the system: disappears and reappears by itself?

the first thing i was going to check on is the pedal excenter/spring. this mechanism helps the pedal come up all the way and aids when depressing it, right? i didnt creep in there on my back yet, being afraid i would need a chiropractor when done.

 

apparently the old MC has a small plastic retainer that holds an o-ring on the end of the piston ...and it is this plastic that can become brittle, or not properly retain the o-ring. This is what I've researched.
So I change the MC on my 08 pre-emptively, because its cheap and easy vs waiting for a potential failure/issue.
I also reused the original translucent reservoir (but with new cap) so i can actually see the colour. I 'ranger' several times each season...its amazing how quickly the fluid absorbs clutch dust and goes dark

good luck

 

interesting, thanks.

btw, my fluid is perfectly clear. i have not touched it since i own the car (>5 years).

 

Still a good idea to change the fluid as the fluid breaks down over time. Recommended clutch fluid change is every 2-3 years or 30,000 to 45,000 miles.