I've been trying to get the clutch on my 85 bled. I'd like to see if I can get a consensus of the best angle to have the car at when you're bleeding. I figure the angle of the car can be changed to move the master, since you take the slave off and hold it at it's own angle.

So, nose high, tail high, or level?

Thanks,
Bill

 

If you are going to squirt brake fluid out the bleeder on the slave, you want the slave to be the highest component in your brake system. You want air bubbles to move to where they naturally want to move, UP. C4 clutch systems don't bleed well. Last time we did it to my 87, we finally gave up and in two days of driving, the air went out of the system overnight by itself and I noticed a hard clutch pedal the second morning. Another way to bleed the clutch system is to feed bubble-free fluid into the slave bleeder and pull a vacuum at the master. This way air bubbles move along with the fluid UPWARDS.

 

I've bled my clutch everyway but the right way. the only thing that has ever worked was to power fill it from the bottom, through the slave bleeder screw. worked like a champ.

 

I've tried it up from the bottom about 5 times, and still no luck. Is there any trick to getting a good seal for the hose on the bleeder? It starts weeping at about 5 psi, and I pump it up to 10. I'll get fluid out of the top, and it doesn't seem to have any bubbles. I've also slowly pushed the slave piston in while I've had it pressurized just to make sure there was nothing in the slave.

I wonder if the air is getting caught in the little kink where the top of the line turns down to go into the top of the master. It seems to me that things would work out better if the line went in the bottom. Regardless, I'm still stumped.

 

I used a soft clear plastic hose, 5/16th inch inside diameter. it fit very snuggly over the bleed screw. being clear, it was easy to monitor for any entrained air bubbles. also used dot 5 silicon brake fluid because it preserves the hydraulic seals much better than dot 3 fluid...also more expensive.

 

MT,

If your bleeder had a pressure valve, how much pressure were you running?

Thanks,
Bill

 

Quick question....did you replace the clutch?

 

It has a fairly new clutch on it, but the problem didn't start following a clutch replacement. When I bought the car it had no trans in it and came with 2 halves of the 4+3, one of which was broken (the 4-speed section actually). I decided WTF and I'd just go ahead and put the TKO kit in it. The previous owner didn't open the hydraulics when he pulled the tranny, so I left it alone and reattached it. It worked until one day when I decided to run some errands in it. I went to back up the driveway, and it wouldn't go into reverse. I was able to get it into gear by turning the motor off, shifting into gear, then starting the car again. The friction point was noticeably lower, but I was able to modulate it enough to park it in the garage. There was evidence of a MC leak, so I just went ahead and replaced the master, line, and slave all together. I haven't been able to get enough clutch pressure to get it in gear since.

A long answer to a simple question, but I really do appreciate the help.

Thanks,
Bill

 

The 85 slave has a chamber/pocket in the rear where air is tuff to remove..... but it can be done....

if worse comes to worse, take it off and bench bleed it submerged in fluid.... at least you can see if bubbles are present with the bleeder off and then install the bleeder and fitting while submerged.


I put a SS braided line on mine with a speed bleeder on the bleed end,,, and rolled the slave in my hand while the pedal was pumped, I even smacked it several times with a block of wood to shake free any bubbles,... it finally bled all the way after pushing a full large bottle of fluid thru it,.... I then shut off the speed bleeder and it was done.

 

my pump didn't have a pressure gage; but as I said, the hose fit very snuggly and would hold any reasonable pressure, certainly more than the 10 psi you mentioned.

 

Has anyone tried vacuum bleeding the system through the release cylinder bleeder? Does the orientation of the cylider still play under the vacuum bleeding method? It probably does. I used to have a pressure bleeder as well and I may have to dig it up.

I did it once last year after I had to replace my release cylinder and it seemed to restore the pedal to normal. Recently, the pedal feels a bit squishy and I have noticeably use more effort to get it into 1st and especially reverse. I'm going to vacuum bleed again but I also decided that given the age of the master cylinder I will replace that as well.

 

Last night I pressure bled the slave by itself on the bench while hitting it with a rubber mallet. I made sure to keep it upright as I attached the banjo bolt. I then filled the system with the power bleeder through the slave's bleed screw, again whacking it with the mallet. I think the pedal is a little firmer, but that might just be wishful thinking. I have seen some people on here say that driving the car helped, so I may dedicate 30 minutes or so each day to letting the car idle in the garage while I slowly pump the clutch; maybe it will come back before I need to tow it to the storage unit on Friday.

I'm starting to get the feeling that the solution to this may be dropping the tranny to put in an aftermarket concentric slave setup on there and then attaching an LS motor to the bellhousing to close it off. Might be something fun to do when I get back from A-stan.

 

Alrighty...try this. Remove the rod between the clutch and fork. See if you can get a hard pedal with the slave piston all the way out against the clip. Be careful with the pressure you apply to the pedal, or you could blow the clip out of there. If you get a stiff pedal, you have no air in there and your problems lie elsewhere. You can push the piston back and forth slowly (at any angle, preferably with the fitting all the way up) to try to remove any air. Be sure to watch the fluid level so you don't overflow the master. After a flywheel turn and clutch replacement on my 85, I replaced both the master and slave, tried every bleed method known to man, (except upside down under water), and could not get the clutch to push in far enough. I ended up lengthening the rod a quarter inch or so, by sawing off a 8mm ball driver and replacing the stock rod. You say yours was working before, but if you get a hard pedal by trying what I have described and still can't get the clutch to go in far enough (the test being reverse), you might try it. You can always put the stock rod back in if it doesn't work. You could have some pedal pivot wear, which is not allowing the clutch to go in far enough. This could explain the deterioration from working to non working.

 

Thanks for the suggestion, Powerpigz; I figured the worst I could do is blow my clutch so I went to Lowe's, got myself some 5/16 rod and made a pretty reasonable copy of the rod, just slightly longer. It was long enough that the slave was just slightly short of being up against the back of the cylinder. No change; which I would have guessed given the theory of operation of a hydraulic clutch, but it was worth a try.

Here's another question: What's the chance that either a: the master is underbored, so it'd not moving enough fluid for the slave or b: the slave is overbored, so the fluid volume increase in the slave doesn't result in enough linear movement?

Thank you all again,
Bill

edit: I guess I should have specified, I did get rock solid pedal with the slave up against the stop.

 

I would guess the overbore theory is plausible, if you maybe had the wrong parts in there.(if that is possible). I agree that the stroke must not be long enough. I suggest checking the pedal pivot wear at this point. If it has much more of an inch of slop before it moves anything down below, then repair may be needed. Not fun.

 

I assume you're talking about the pivot where the end of the master cylinder plunger attaches, correct? There's a little bit of wear and maybe about 1/2 inch of free play in the pedal before it starts moving the plunger. I had a heck of a time getting it to fit over the end of the pivot, so I think it's tight.

I may just drop the $90 on a new slave at NAPA, since that's the only part I haven't tried 2 of.

 

The pedal slop sounds about right.....I am curious to know how far the slave rod is actually moving the pressure plate arm? I do not know what this measurement should be, but maybe that could be looked up......I am assuming if the slave was bad, there would be a leak.....

 

The last time I was under there with someone on the pedal I'd say it was moving about 3/4 in at the slave.

I started unbolting it to see what removing the firewall spacer would do last night, then decided to can it. I opened up my old master, and I think I may be able to create an adjustable pushrod that I could put in the new master. That way I can work with the full potential travel of the master which should translate down below.

If I don't get it driving tonight, it get's trailered to storage tomorrow and waits for the end of my deployment.

 

I would guess that 3/4 of an inch would be enough to disengage that sucker. I was going to suggest that number, but was not sure enough about it to suggest it. It seems to me if the fork is moving that far, you should have some sort of disengagement. I am trying to remember from 3 years ago, when I was going through what you are going through. Spacer thickness on the master, or what you are going to try are things I did not try.

 

didn't want to go here, for fear of misleading or confusing forum members, but hey, what the heck.

with the stock spacer my clutch pedal went to the floor, and I mean the floor; mat removed etc., before releasing, driveable but not right.

fabbed up a bunch of thin spacers. when the mastercylinder is moved in closer to the firewall, the pedal moves closer to the driver and allows the piston to move in deeper into the bore of the master cylinder before the floor stops the travel of the pedal.

with the trans still out I was able to measure the actual travel of the throw out bearing. ZfDoc says the throw out bearing travel should be in the range of 0.291 to 0.310 inch. With the stock spacer the max travel I got was 0.221; with a stack of spacers approximately one half the thickness of the stock spacer, I got a max travel of 0.285 with some (minimal) entrained air when I power bled the system (used clear soft plastic hose so I saw what I saw). so once this small amount of air escaped up the clutch hose into the master cylinder through use, I am certain that I was within the 0.291 inch range.

in any case, 0.285 was close enough. great pedal, great engagement, no clutch issues.

an unexpected benefit was that the clutch pedal moved towards the driver and is now even with the brake pedal. before it was decidedly lower than the brake, which always struck me as somewhat clumsy or odd at best.

the factory service manual doesn't address the spacer thickness issue, but does make the cryptic suggestion to "check for bent clutch pedal".

good luck. stay safe.