LS1 clutch not engaging

[gdr]

I've got a clutch problem in a 2000 LS1 5speed that the dealer has been unable to replicate.

About a 2 months back I was highway driving and, slowing down as I was coming into
the city, I found that I had no clutch; I put the clutch to the firewall but didn't feel
any of the resistance that you would normally get at the friction point and and to
force the gear shift out in order to stop. A bit of experimenting I found that I could
sometimes get the clutch to engage a bit by rapidly pumping it. After limping into
the dealership and leaving it with them they reported that they couldn't find a problem.
The suggested that a loose floor mat may have gotten behind the clutch and therefore
I just wasn't pushing it in far enough. I doubted it, but told them I'd hold onto the car
until it happened again. And it didn't until last Sunday.

Once again I was out on the highway and experienced the same problem. I again
limped back to the city (late) and the next morning took it to the dealership. The
following morning it wasn't as bad (ie: with a cold vehicle) but it was still noticable.
I just got another phone call saying that they couldn't replicate the problem, even
after someone took the car home for the night (about a half hour drive, mostly highway)
and brought it back in the morning.

The dealership has done a visual inspection, has checked fluid levels, etc, but I'm
under the impression that they only half-believe my problem description, and even if
they do they apparently can't replicate it. Other than the obvious of getting a mechanic
out with me when it occurs, does anyone have any suggestions on how to proceed,
or suspicions as to the cause?

Ambient daytime/evening temps are 20C/5C currently. When it happened originally
they would have been slightly below freezing (-10C to -20C).

[spork]

I never had my clutch fail completely like that. It was not fully dis-engaging and caused 5th gear to get ground up. Under warranty, they replaced the slave cylinder and the messed up gear.

[zoomboom]

I had exactly the problem described by GDR about 6000 miles ago on my low mileage 2000 LS, also following a long run on the highway. A (conveniently) nearby Saturn shop bled the clutch hydraulics to get me back on the road, but couldn't pinpoint the cause. My regular dealer was no more successful in isolating the problem. One dealer suggested replacing the slave cylinder, another suggested replacing the master - neither expressed any confidence in their diagnosis. Without a clear culprit, I replaced nothing and have continued to drive it, a little nervous about the possibility of killing parts of my gearbox.

My clutch still occassionally doesn't feel right on a cool morning after the car has been sitting for a few days - the clutch will engage low. On those rare occasions, a few pumps of the pedal brings the clutch action back to normal. I have a hunch (completely speculative) that there may be a flakey seal on my clutch master cylinder.

I believe there was a TSB concerning improperly lubricated clutch pedal pistons on the master cylinder causing pedal squeak, and I wonder if that could lead to failure of any seals in the master. My pedal sometimes squeaks in warm weather, a phenomenon that my dealer never was able to observe. Anyway, my clutch remains a mystery.

GDR, if you get yours properly diagnosed and repaired, please post the results. Good luck

[IMkenNY]

gdr, if your not not seeing any fluid loss its most likely the clutch master cylinder failing.