Bleeding Hydraulic Clutch

c_forshaw · #1 (**permalink**) 10-27-2001, 07:17 PM

I have replaced the Slave Cylinder on my Hydraulic Clutch. Now how do I bleed it?

poorboy · #2 (**permalink**) 10-27-2001, 07:46 PM

c-forshaw;

Not knowing what type of system you have I'll just give you a genral idea. Fill the master cyl. resvior, , push the clutch peddle down and release a couple of times(not to fast) hold down peddle, open then close bleed screw release peddle. You may have to do this a few times. DO NOT LET THE RESVIOR RUN DRY!!
It will take 2 people to do this.

Poorboy

dalola · #3 (**permalink**) 10-27-2001, 08:57 PM

c,
Keep in mind, it's basically just like bleeding brakes. You can do as poorboy instructed, or better yet, if you have access to a vacuum bleeder, such as the Vacula, it works excellent for clutches, and makes it a one man job. Remember to use brake fluid in there as well. Depending on pipe routing, you can also use the old tried and true gravity method, if you're not in a big hurry!
Dave

Bob Putnam · #4 (**permalink**) 10-28-2001, 05:13 AM

And always check that the bleeder is at the highest part of the slave when bleeding. That may mean that you might have to jack the car up only at one end or the other.

c_forshaw · #5 (**permalink**) 10-28-2001, 06:44 AM

How do you do the gravity method? I've seen it mentioned several times.

427sharpe · #6 (**permalink**) 10-28-2001, 07:46 AM

Gravity bleed--just open the bleeder screw alightly and let it drip out, keeping the master full at all times. Gravity pulls the fluid which will displace the air sooner or later. My .02 says use a one man brake bleeder, faster and cleaner. You can buy one @ AutoZone/PepBoys for about 10 bucks. Or make one by slipping a piece of vacuum line over the bleeder screw (make sure it's a tight fit!!) and putting the other in in a container of brake fluid (make sure the container is BELOW the level of the bleeder, and the the end of the line stays BELOW the level of fluid). Open the screw, fill the master and SLOWLY depress the clutch pedal 10-12 times WITHOUT letting the master run dry. Tighten screw. Try clutch. Repeat as neccessary. Drive. Have fun. Embarass Chevrolet's. Make whoopie.

c_forshaw · #7 (**permalink**) 10-28-2001, 09:40 AM

Thanks for all the help. Got all the air out and strong pedal (with the wife’s help!) One more question. When I replaced the slave cylinder, I can’t remember if the mounting bracket was on the front side of the block/bell housing or on the rear. How far should the release lever assembly/TO bearing depress?

Bob Putnam · #8 (**permalink**) 10-28-2001, 03:09 PM

You need to be able to adjust the clutch rod so that the slave cylinder piston is about 1/4" from being bottomed out just as the clearance between the throwout bearing and the clutch fingers goes to zero. You'll have to open the bleeder and push the rod as far as you can into the slave cylinder. Holding the rod in place, adjust its length so that there's 1/4" clearance between it and the throwout fork.

Unfortunately, I don't have a diagram right now. If this is unclear, I'll come up with one tomorrow.

Mike Braddock · #9 (**permalink**) 04-26-2002, 10:45 AM

Bob,

Why do you adjust it so it's a 1/4" from the end of it's travel? I'm very interested in hearing the reason because we just bled our slave cylinder but don't have enough stroke to release the clutch. We have a mild spring between the throwout arm and the slave cylinder that maintains slight tension on the pushrod to prevent it from falling out.

Now I'm wondering if that spring is actually causing the throwout arm to push the slave piston all the way back in the cylinder thereby reducing the effective stroke of slave cylinder. I was planning on trying to adjust the pushrod so that when the clutch is released there is about 1/16" clearance between the slave cylinder piston and the end of the cylinder so the clutch fork does not keep the throwout bearing in constant contact with the diaphram fingers on the pressure plate. But you say adjust it so there's about 1/4" instead?

I'm going to check tonight that we got all the air out of the line. We had the same master and slave cylinder piston diameters but a long style clutch in the car previously and the clutch worked fine. But perhaps the diaphram style clutch needs more travel to disengage?

Mike

Mike Braddock · #10 (**permalink**) 04-29-2002, 12:20 PM

I checked the clutch and it appears we did get the air out. I bled it a few more times and the pedal feels the same and the clutch still won't disengage completely. I'm going to try adjusting the pushrod next and if that doesn't work, I have a 7/8" master cylinder that I will swap out for the 3/4" one we're currently using.

Mike

Bob Putnam · #11 (**permalink**) 04-29-2002, 12:54 PM

Mike,

If you use a return spring, ignore my 1/4" recommendation. I like to allow the slave to act as an automatic adjusting system. You're setup is OK, but you'll have to keep a close eye on the clearance. As the clutch wears, the clearance will go away - and initially it will change fairly quickly.

Mike Braddock · #12 (**permalink**) 04-29-2002, 07:03 PM

Thanks Bob. This evening I went back down, cracked the bleed fitting on the slave cylinder and let gravity take over. After about 15 minutes...whala. Now we have a nice feeling clutch pedal. I also bled a little more air out of the clutch master cylinder and the clutch is releasing fine. But it releases about 1/4" from the end of the pedal's travel. Is this okay, or will I put accelerated wear on the syncros? I have a 7/8" MC I can swap in the 3/4" MC's place, but the pedal effort is so low now it's great. I can easily depress the clutch with my hand; the effort is about the same as my Nissan pickup truck

. On the other hand, I certainly don't want to cause any problems by not disengaging the clutch far enough, so would you suggest I swap in the larger MC? I'm not sure how to check this aside from waiting until I can drive the car and see if it goes in and out of gear easily. Even then, is that a good enough indication, or would I be wise to swap out the MC for a little extra slave travel? Thanks!

Mike

Bob Putnam · #13 (**permalink**) 04-30-2002, 05:16 AM

Mike,

You're asking for long-term trouble with so little extra stroke. If the clutch is that light, I'd change to the 7/8" master. Better safe than sorry.

Clois Harlan · #14 (**permalink**) 04-30-2002, 06:12 AM

I fought this for days before I found a leak in one of my stainless braided lines. I also ran my bleeder line up the back of my bell housing so I could attach a rubber clamp and terminate my bleed line at the back of my engine on one of my top bell housing bolts. It is much easier to bleed out the air standing up and even easier with a vaccuum bleeder. Good luck.

Clois Harlan

Mike Braddock · #15 (**permalink**) 04-30-2002, 07:54 AM

Bob,

Yeah, that's what I'm thinking too. I just wanted a second opinion. Thanks for all your help in this thread! Clois, good idea about the bleeder line. I have an access panel cut inside my footbox so I can access the bleeder quite easily.

Mike