Bleeding the clutch on a C4
 

Ok, I have tried gravity bleeding , reverse bleeding, pumping and bleeding. will go into gear once or twice afterwards, then it will not anymore. replaced slave and master and still no difference. I never thought I would say this and forgive me, but I am starting to really hate this vette. :toetap: and other ideas I should try? Thanks in advance

I actually just did this yesterday after replacing my clutch hydraulics. Some shifts started fighting me. It should shift with little effort. If it's air in the clutch hydraulics and it doesn't want to go into gear you should be able to hit the throttle until it goes into gear when you hit the magic rpm number.

What did you reverse bleed with? As far as I can tell reverse bleeding this system is the only way to get the air out. This is the tool I used:


It may be a little overpriced for what it is but they have a patent on it and it works. My shifts are much easier now.

Pump it up then hold it for a few minutes then let your foot slip off to the side letting it spring back. Do this many times tonite waiting a few min in between and keep it full. Then let the air settle out and do it again in the morning. Then drive it and do it daily till it is good.

I tried the old pump oil can and a hose as suggested by someone, But I may order the phoenix pump.

I did try this method, but will try it again.

The system is self-bleeding -- which means it should correct itself WITH DRIVING. Of course, you have to manually bleed until it's at least "driveable".

When mine was still "imperfect" as simple pumping to bleed, I took it on the road pumping downhill, pumping uphill, and on level surface. The idea is to get any air bubble near the connecting hose...so it will travel up to the master.

Mine actually self-bled after only a few pumps alternating the incline/decline...which btw is something you should consider during gravity/reverse bleeding....getting the end of the slave cylinder (with the feeder hose) higher with respect to "level".

Reverse bleeding should work just fine, followed by 50 or so pedal pushes should give a firm pedal. You can monitor air escaping the clutch master reservoir by recording with a smart phone. Pump the clutch 15 or so times while recording and then watch the video to see if air is still escaping. If so, keep repeating until no more air. It should be pretty obvious.

If replacing the slave cylinder the best way i've found is to pre-fill the salve through the feed port before installing (bench bleed). Carry it over to the car, unbolt the previous slave, remove the clutch line and swap the new one on. If the master cylinder fill cover is installed very little fluid should escape the clutch line when swapping slaves. 20 or so clutch pedal pushes (varying stroke and frequency) should self bleed the rest of the system.

I tried every way but the right way to bleed the clutch on my 96; Finally got a new / clean, grease gun, filled it with brake fluid, got a few fitting at the local ace hardware and some clear plastic hose, (the grease gun threads are 1/8th inch pipe threads), a 1/8th male pipe thread to 5/16th inch hose barb, clear plastic hose which also fit tightly over the slave bleeder screw, shot the slave cylinder through the bleeder valve, and in five minutes had my clutch back. 5 minutes versus five days. the choice is yours.

well I finally got it bled. still will not go into gear while car is running. when I turn the car off and put it into gear and start the car, it will lunge forward a bit. I am thinking the clutch got toasted somewhere along the way, but I am hoping thats not the case

what year?

in the olden times, I'd say your clutch rod needed adjustment...but I don't think that's been an option for quite a while. But along the same lines, at least with LT pull type clutches, using a narrower spacer than the stock one between the clutch master cylinder and the firewall will increase the travel on the piston in the master cylinder = more displaced fluid.

sounds to me like the clutch isn't disengaging fully..(as contrasted with "toasted clutch" which will disengage but lacks enough clamping pressure to transmit torque)....yeah I know that could be , and hopefully is, a hydraulic issue, but what I have seen on diaphragm style clutch pressure plates, is that one or more fingers may have broken off, resulting in a clutch that can't disengage; throw out bearings, clutch forks, ball pivot studs are all suspect too.

It is so odd that this same set-up was running perfect before the swap. I am just tempted to take out the trans and check everything out, but really hate to tare everything out because its a convertible and i have ro remove all the x braces and crud to get that sucker out

Glad to see someone else recommending this, it works which is why I mentioned it at that time. I had the mc and slave changed in mine a couple of years ago and they could not get the system bled 100% of air. Talking to a former co-worker who was once a Chevy mechanic, he recommended this: Take the cover off the mc, insure it has sufficient fluid, bleed it as defined, now pump the clutch 6-10 times rapidly and hold it for about 5 minutes then slide your foot off the pedal and let it pop up on it's own. The thinking is that any air in the system will work back up the line to the gooseneck over the mc while holding the pedal. When the pedal is released, the back pressure from the slave will push the air back out into the mc. Might have to do it twice but that took care of mine and I spent a lot of time trying to bleed it before and failed. This worked for me.

What antfarmer suggested works. Read this thread:

https://www.corvetteforum.com/forums/c4-tech-performance/3817171-clucth-hydraulics-2.html

If it's properly bleed and still grinds or won't go into gear you may need a thinner plate between the firewall and the master cylinder.
I've had to do this on a few c4s.
Usually. 125-.175 is enough to move engagement to roughly the middle of the clutch throw.

If you need a thinner plate I have a few for sale.

I did the pump and let foot slide off, what seemed to work was the reverse bleed and the ant farmer method together. My pedal is now nice and firm with no play in the pedal. but i still have the same problem. I can put it in gear and start it but the car moves when it starts, but cant do anything while its running, if i try to force it, car seems to move and sometimes i will get a grind.

I have the plate off of the 95, I will compare the thickness and see if they are different

What are you troubling for exactly?

Its just not going into gear. its as though the bearing is not releasing enough to allow the clutch to work correctly. I adjusted the plate behind the master and still no change, so I am going to take the damn thing out and see what its issue is

anyone want to buy a Vette? LOL

Could it be the time for a new clutch kit?
and some clearance check