I drive my C5 daily and have had very few issues with it. I went to go to work this morning and damn near drove the car into the kitchen. When the car was started in gear it lurched forward. Luckily the e-brake was on, and i had my foot firmly on the brake when i started it up. After it stalled, I put the car in neutral and started it back up. The car will not go into any gear. Doesn't grind, but just will not go. the car tries to move forward when trying to put it in first.

The fluid reservoir is full, I even sucked out and changed some of the fluid with fresh fluid. The pedal seems somewhat soft, then gets stuff towards the bottom. It springs back properly.

Any ideas? I am supposed to sell the thing on Saturday.

 

Sounds like maybe the clutch master is going south. Usually, if its the slave, it will leak. But you say the master was full..... How many miles on the clutch hydraulics?

 

Possible slave issue. Need to get underneath to see if it's leaking, etc.

 

86k on the car. No leaks under the car that I saw with a quick glance.

 

I think a little closer inspection is in order.

 

I'll take a closer look when I get home. If there are no evident leaks, what is a good way to narrow it down weather it is the master or slave, since I am fairly convinced it is one or the other?

 

Lets just say that the master cylinder is MUCH easier than the slave. The slave will take 8-10 hours to do. The master cylinder will take a couple of hours maximum.

 

Not necessarily, my slave cylinder was damaged (internal scoring) and it never leaked.

 

Thats why I wrote USUALLY.....

 

I have been having issues with my clutch and trying to get help on the beard and so far haven't figured it out. Mine has started doing the same thing lately as well as not being able to disengage the clutch under heavy throttle. Everyone said Master, Get a tick, slave, but I could get how it would grip to no end but not release? Now about a week ago mine did this exact thing you are describing, but I wasn't gonna leave my car or have it towed if not needed. I bled the hydraulics over and over and repeatedly changed fluid till clean and kep doing the same thing.

How I have remedied it so far 4 times? Get the car back from the garage a little more, put it in 1st and while clutch in , fire her up and let her do the lurch forward thing and she'll give after a few feet and "unlock?" whatever is bound? About as harmless as starting an older manual tranny car without clutch lockout while the car is in gear and clutch out. The starter and flywheel take the blunt of the work and the car will "lurch" forward till she fires up and takes off.

I just wish someone can clue us in as to what needs replacing other than throwing parts and time at the car. I have done 2 masters (new) one made adjustable, as well as removing the exhaust and checking the clutch, PP, and slave and all looked well. I had a theory of the clutch being too worn and the slave being extended fully and not enough to release the clutch, but this theory was shot down. The clutch looks decent and grabs hard as hell, so I still don't get it. It's whatever force opposite what it takes to engage the clutch messing up? Whatever that is? I even watched the slave in action under the car and cannot see a problem other than harder to get in gear at idle and impossible to shift gears under throttle.

 

You will never see a clutch master or slave cylinder bypass internally. Everything looks fine on the outside, but inside the rubber seals are bypassing fluid causing less hydraulic pressure on the pressure plate fingers, which in turn isnt giving full release of the disc.

Its the same as when a brake master cylinder is bypassing internally. When you sit at a stop light with your foot on the brake and your foot slowly goes down towards the floor, its bypassing internally.

The difference in a clutch master is that you wont feel your foot go down because its planted firmly on the floor.

 

Welp, local Corvette shop is saying it's the clutch. There goes $1,300 I don't have.

 

New clutch, flywheel, slave and pilot bearing en route. I trust the shop, but I am going to ask to see the clutch after they pull it out just to confirm, that somehow overnight, in the garage it self imploded. FYI, I went with an LS1 clutch and flywheel instead of an LS7 one since the shop seemed wary of installing those, saying it needed a different master. I am selling the car regardless, so I don't care if it has one or not. If it were up to me and the shop would warranty the work, I would have gone to autozone, lol.

 

Got the car back last night. Got the new clutch in. Old pressure plate had some issues.

 

Having the clutch 'break loose' when it is started in gear is a sign of the clutch facing sticking to the flywheel or pressure plate. Some brands of facings are more prone to do this than others. If your car sits for a few weeks, it can rust to the flywheel if the weather is just right (or wrong in this case). It's a very common problem for tractors to do this in the springtime. I have seen them stick so bad that they had to be chiseled off. Sometimes you can break them loose. If that's not the problem, another possibility might be the center hub in the disk being worn & loose - not the spline, but inside the disk itself. This would allow the disk to wobble and drag against the flywheel & PP. It doesn't take much since the PP only moves about .050" to release the clutch. If it was hydraulics, it would not correct itself.

 

You paid $1300, have 86k on the car, and the shop used the old pressure plate??? That's BS! You should have went with the LS7 kit. As long as you use the LS7 PP, Disk, and Flywheel it will work. Upgrade the slave and master to the LS6 style.

I would be pissed..

 

No. Got a new pressure plate, clutch, slave cylinder and pilot bearing. I meant the old pressure plate had some issues, thus causing my original problem.

I didn't go LS7 kit for 2 reasons: 1. I'm selling the car, so I don't care if its upgraded. And 2. The Corvette shop didn't seem confident in putting it in trouble free, despite the countless threads saying otherwise on this site, so I was afraid they wouldn't warranty their work should something be amiss.

 

Bringing this back, this just happened to me in my 04. To back into a spot, I pressed the clutch pedal fully, put the car in reverse, started depressing whole very lightly giving gas. Car backed up a foot or so while the clutch is still engaging and I heard a 'clink' from under the front of the car and the car jutted backwards. I depressed the clutch fully and the car still moved backwards as if the clutch was fully engaged. So I pulled the shifter hard into neutral with the 'clutch depressed'. Then it would NOT go back into gear with the car running. Turned the car off, checked for a puddle or drips under the car, nothing. The clutch now has a bit less pressure in the beginning of the pedal range, and has some clicking sounds. So, based on previous experience on other chassis non-chevy, it sounds like a clutch master cylinder problem. The car is low and in a parking lot safe at the moment. Are there any other diagnostic tests I can do to tease out what the issue is before getting it on a tow truck or lift.