LO PHAT

I am hating my 1998 Corvette's clutch. For the past few months it simply hasn't felt or behaved like it should.


Here is what I notice:

1) It seems to take excessive force to select a gear, and it also requires a lot of force to return to neutral. This occurs most of the time, especially in 1st through 4th gears. On rare occasions it will almost feel like I am locked out of a gear, at which point I can either force the issue or simply move to the next gear.

2) The clutch often sticks to the floor early in the morning (about a few miles into my commute to work). I am 100% certain that this is NOT a high RPM shift issue as I rarely go past 3,000 RPMs when the engine is not fully warmed up! I also do not believe this to be a fluid issue.

3) The clutch starts to engage at (maybe) an inch off the floor. In contrast to my Z06, this seems very low in the pedal travel. I do not view this to be a bad thing, however, if it is considered normal for some cars.


Here is what's been done:

1) The clutch fluid is kept very clean using the "Ranger method."

2) The transmission fluid was replaced with Royal Purple oil less than 3,000 miles ago. (This made no difference.)

3) I aligned the shifter about two months ago. (This made little difference.)

4) About two years ago the entire transmission was rebuilt with new parts by a professional shop. A new clutch was installed at that time. The shifts were amazing for the first year or more.


I'm looking for suggestions and thoughts here. Any light you can shed on this issue would be most appreciated. I don't want to start just wildly throwing money at things hoping for a fix.

Thanks,
LO PHAT

squidwards vert

Torque Tube bushings?

C5 LS7

Air? Try bleeding w/ vacuum. Get a #10 rubber stopper w/ 1 hole in it from your local scientific supply house ($2.00), get a hand held vacuum pump w/ a gauge on it. Make sure the reservoir is about 1/2 full of fluid, insert vacuum hose into top of stopper and place into top of clutch fuild reservoir and apply 15 to 20 inches of vacuum. Bubbles will start to rise out of res. at about 15 inches, this is the fluid boiling and the air is leaving the system into your vac. pump. Cycle the clutch pedal 8 to 10 times while keeping the vac above 15. You will probably find the fluid getting black in the res. clean it w/ the Ranger method repeatedly, keep pumping pedal until it stays clean. maybe 15 or 20 minutes. Now ALL the air is gone, see how the car shifts. I have been having some problems w/ my clutch and a couple of Forum members recommended this fix. It works, I use a Mity Vac and love it. Good luck!!

coolbubba

Replace the clutch master cylinder...the stockers are not known for longevity.

Eric D

Before replacing anything try this method, it works.

Bob25thTA

Also look at Clutch pedal return spring, found mine broken. 03 C5

Atok

My guess would be a bad master cylinder.

LO PHAT

OK ... I borrowed a Mityvac from my neighbor and ordered a #10 rubber stopper with one hole from an online store. Hopefully the rubber stopper will be here in a few days. I'll let you guys know how this turns out.

Thanks to everyone who posted!

LO PHAT

huttler

What online store was it? I need a rubber stopper too

ipuig

The only correct way to bleed the clutch's hydraulic system is to perform the procedure outlined in the GM factory shop manual (bleed it from the slave cylinder along the same line you would bleed your brakes).

LO PHAT

I need your help, guys.

This morning I put vacuum on the clutch system as described above, and my wife was working the clutch pedal. She was able to get only two pumps on the clutch pedal before it started sticking to the floor. I had her pump the pedal a few more times, and each time she had to pry it off the floor with her foot.

At this point my observations were as follows: 1) I removed the vacuum and observed some bubbles rising 2) there was no change in fluid height in the reservoir

I then changed the fluid in the reservoir and repeated the process again. Now there was no clutch pedal (it stayed on the floor every time). At some point I started hearing a lot of bubbles (and I mean A LOT of bubbles!) in the reservoir. This worried me, so I removed the vacuum, changed the fluid again, worked the clutch pedal until it stopped sticking to the floor, and took the car for a drive.

What went wrong?

LO PHAT

rich65

Any answers guys cause i'm thinking of trying this also . Is there a diy on here somewhere also ? Any special place to get all the stuff needed would help to . Thanks

Eric D

Couple of things, first off keep the cycling of the clutch petal slow, no more then about 15 to 20 inches of vac, expect the fluid to boil with the vacuum on it. Add fluid as needed to the reservoir if it become low. Did you notice any improvement in the clutch operation? If not, there maybe other issues with the master or the slave.

Chevy Nick

Get a Tick Master Cylinder, and put in a remote clutch bleeder next time you're in there.

C5 LS7

You need to do the vacuum for at least 15 to 20 minutes. The clutch pedal will not return from the floor while you are hitting it w/ vacuum. after you have worked it for 15 or 20 minutes, stop working the pedal, run the vac to 20 in. and let it go to 0. Now try the pedal, it should work well, if not you have a different problem. I am running a Tick master, GM slave and Mcleod RST twin, I don't even use the bleeder any more, I threw away my remote bleeder. If you are having problems because of air in the system, this will work well. Eric D works for GM, this is how they do it, Mcleod clutches use the same method. Don't give up.

Rick

LO PHAT

So should I be pulling the pedal off the floor and pushing it back down repeatedly during the recommended 15 to 20 minutes? Am I keeping constant vacuum on the system the entire time, or do I remove it occasionally to properly work the clutch pedal? How often should I cycle the clutch during the period of vacuum?

LO PHAT

Bull_in_a_china_shop

I would replace the hydraulics. The slave I believe is typically whats bad, but its a pita to get at. Replace the master cyl first. Its easy to get at- remove the drivers wheel well shroud and pop the old one out. If all that dont help *gulp* on to the slave.

C5 LS7

Lo Phat, Yes, you should be pulling the pedal up off the floor slowly while the car is under vacuum, move the pedal in and out 10 times a little slower then you would do if you were shifting in traffic, the Mity Vac I use has about a 2 gallon tank, so it does not run out of vac quickly, I do this proceedure alone. The vac goes from about 20 inches to 15 or 16 w/ 10 pedal cycles in my car. Pump up to 20 inches, do 10 cycles on the pedal, then pump the vac back up to 20, let it bleed down to 12 or so and pump it back up, and let it bleed down again to zero, repeat this for 20 minutes. Try the clutch, if it does not work, start thinking, slave, clutch and master replacment. I just put in a Mcleod RST and it works great.... How many miles on the clutch? Do you launch hard in first gear? Drag radials? Mods to engine?

LO PHAT

- 16,000 miles
- never
- never
- Blackwing intake and Borla mufflers only


LO PHAT

ipuig

With all the time you are wasting performing these off the wall bleeding procedures you could have lifted the car, removed the center exhuast and tunnel plate and bled the system as it should be bled, (from the bleed fitting on the slave cylinder). If you continue to pull vacuum on the system you will most likely continue to introduce air into the hydraulic system and not correct the issue.
Instead of listening to all of the internet experts, I recommend you perform the manufacturer's bleed procedure and conduct a proper visual inspection of the slave cylinder actuator operation. You should be checking for leaks and that the actuator stroke distance fully disengages the pressure plate from the clutch disc when the pedal is depressed. You can visually inspect the slave cylinder operation by removing the lower bellhousing inspection cover.
Imagine that, performing a maintenance procedure as it was meant to be by the engineer who desingned it, what a concept! Good luck.