1996 lt4, zf6. Rough shifting. Oddly, the clutch pedal is nice and firm. Clutch bites at the correct point. I removed the slave cylinder. Put a borescope down into the bell housing to see if the clutch fork was bent. Basically, to see if anything was out of the norm in there. Fork is not bent, pivot ball stud is in place as well. I can post pics of this if needed.

I've asked two local corvette shops in person about bleeding the clutch hydraulics. They both told me the clutch reservoir will always have bubbles in it. Is that true?

Very novice questions:
1. Does bubbles when pumping the clutch pedal indicate air in the system?
2. Will air in the system cause rough shifts?


New clutch line. From zip corvette, I believe? Lines are tight as humanly possible. Anything more, and I'll round the heads off them. I do have a question about people that have installed the aftermarket clutch lines. Does it matter which fitting goes the master and slave?

Rebuilt oem slave cylinder by Bill B
New Wagner Master cylinder
Amsoil synchromesh in the ZF.
Rebuilt oem master cylinder by Jim. Not installed. But I do have it sitting in the toolbox.
Tried to explain this as good as possible.

Anything will help, and will be greatly appreciated. Seriously.
Brandon

 

I replaced the master & slave in my 95 coupe a couple of years ago due to severe deterioration of the slave cylinder. In all of my experience it's always better to replace both in a system like this one. My clutch line was in good shape so I just flushed it and dried it out real well. Anyway, when it came to bleeding I first used the gravity method overnight and then applied my vacuum pump to the system. There was still some residual air so I followed a thread posting and pumped the clutch while slipping my foot off the pedal while it was depressed. I did this for around 15 - 20 cycles and that finished off the process. I read somewhere that this system is self-bleeding and the cycling would clear it out. It worked and I haven't had any clutch issues. BTW I replaced them both not due to failure, but surface deterioration and a very black clutch fluid.

Good Luck!

 

There should not really be any quantity of bubbles in the master.

Sometimes the walls of a cylinder can just ware out. Sometimes honing it will work. We did that years ago, no so much today.
Sometimes you just need to replace a cylinder. Could be either. Check to see if the boot is wet or damp on the slave cylinder. If it is dry I would then focus on the master for starters.

 

Q1: yes
Q2: yes, possibly
If the oem master is on your shelf, what's in the car now?
I sent my master and slave cylinders to Jim Jandik a few years ago for rebuild, everything has worked great since. Bleeding these systems can be a chore but not always. Once you get all the air out, flush it every 1-2 years with the Ranger method (look it up) and it should last a long time.

 

Currently the car has a new Wagner Master cylinder. I guess I'll install it this weekend, see what happens.

Nothing is leaking in the clutch hydraulic system. I left the car on Jack stands, and left the kick panel off to see if the master leaks. But as I said, I'll install the rebuilt oem master this weekend.

 

Installed the rebuilt oem master today. Didn't drain the fluid, as it is only a few months old. With zero miles driven. So, filled the master. Pumped the clutch. Had some big bubbles for a few pumps. But after the 50th pump, the big bubbles stopped coming out. So, felt the clutch pedal. Stiff, but not as stiff as the Wagner Master cylinder I removed. Shifted through the gears. Was very smooth, with 5th being not very smooth. Still tho, all other gears were smooth.

But, I knew it was too good to be true. My car is back to rough shifts. In fact, worse than with the Wagner master I removed.

Question. Some have told me to "side step the clutch". Which is when you pump the pedal all the way down, and let the pedal kick back up on its own. Would that not cause bubbles in the fluid? The only time bubbles show up in the reservoir, is when I let the clutch kick up on its own.

This makes me want to get an auto trans C4, sadly.

 

Get a large syringe full of brake fluid and push fluid up through the bleeder. Three times and you’re done.

 

Yes that is how you side-step the clutch for bleeding air bubbles out of the fluid, but you must hold the pedal to the floor for a few minutes before letting it pop up. Probably will need to do it a few times to see any results.

 

This would work-I have done it this way. This way reverse bleeds it.

Shame you are having such a challenge with this car.

Good luck
Steve

 

I bought this to reverse bleed several months ago. Same results with reverse bleeding. At least for me.
But hell, might be worth another try.

 

Reverse bleeding works fine, been doing it with aircraft for 40 years. I've just used a oil can and a rubber hose, nothing fancy.

Sometimes rebuilding just does not work well even if the job is performed correctly. Sometimes a new cylinder is the only cure.

A cylinder might suck in air but not leak due to how the seals sit in the cylinder.

 

I use a Phoenix Reverse Bleeder myself on all my vehicles. It works so very well and is easy to do.

On our 1993 Chevy Pickup with it's V-6 and five speed was always a nightmare when it came time to replace the clutch. We did it several times over the many years we had this truck. When bleeding the air out of a hydraulic clutch the reverse bleeder was "the best, most effective" way to bleed the air out. There were mechanics who brought it back to me and said that there was a problem, he could not get the air out so he removed my brake rod and added a bit of weld on the end to "solve the problem" which it did not. I brought over my Phoenix reverse bleeder and did it right in their parking lot in front of them. You need the right tool for the job, this is it for hydraulic clutches.

I love it on my older motorcycle as it makes the brakes work great by pushing the fluid "up" into the master cylinder. It makes flushing out your Corvettes Brake system a cinch. Air likes going "up" in your hydraulic systems so it makes it faster and easier. The reverse bleeder is able to handle the Bosch ABS units in "Older" C4's as well.