Jeep clutch won't work right--last resort?

Help! I had a new clutch put in my '92 Cherokee Laredo, 4.0 liter, 5-speed, 255,000 miles. I’ve had it back to the shop (good guys, I think) who installed it, 5 (maybe 6?) times now. Clutch works fine for a few days to a couple weeks, then the pedal gradually sinks lower and lower to the floor until you can barely get it to disengage and shift. They said it was air leaking into the clutch hydraulics; first they bled it, then re-bled it, then re-bled it again, then said they read the manual and bled the system EXACTLY as instructed; then they talked with a service guy at a Jeep dealer about any tricks of how to bleed it properly; then last time, they thought they found a small fluid leak in the clutch master cylinder, which they had already replaced once, so sent that back to their supplier and put in a new master cylinder. It was OK for two weeks, then, now, same problem. They (and me) are at our wits end–anybody got any ideas? Thanks a million, petenhisjeep, Wheat Ridge, CO

The problem is likely the clutch slave cylinder.
They should not have attempted to continue beating a dead horse by the constant bleeding of the clutch hydraulics. Logic says the problem is in the clutch master or slave cylinder and both should be replaced at the same time with one caveat.

The caveat is that I think the clutch slave cylinder on this model is inside the clutch assembly with the throw-out bearing. This means if the transmission was removed on an aged vehicle and the clutch assembly was replaced then it should have gotten a new slave cylinder at the time the clutch assembly was changed.
This means back out with the transmission.

They may hit you for labor on this again, but my personal opinion is that this is a lack of foresight on the part of the shop. They’re supposed to think things through a little on every repair they do and cover the bases.
It’s also my opinion that when a transmission is removed on an aged vehicle the rear main seal should always be replaced rather than risk an oil leak 2 days later.

Thank you for those suggestions. The slave cylinder and the master cylinder were both actually replaced, 18 months ago. Right now (today) they are re-replacing the master cylinder–replacing the one they just put in before Xmas, because it does seem to be leaking; apparently it must have been defective, when they installed it to replace the previously defective one. We’ll see how it turns out, thanx again.

Pete(nhisjeep), the questioner, just writing back again. Still haven’t solved this and still having trouble. With yet that latest new master cylinder put in, and another small leak (o-ring) in the hydraulics supposedly found & fixed, I am still having the same problem; after a week or two, the clutch pedal returns to its all-the-way-to-the-floor position before it will (just barely) disengage the gears. The poor guys at Glenn’s Garage don’t know what further to do with it; they (and especially me) would like to have the new clutch that they installed for me, function properly for more than two weeks. ANYBODY got any further ideas? I’ve been browsing all the other discussion posts (there have been many) here on Car Talk, about clutch pedal problems on Jeeps. Thanks again, Pete

Since both hydraulic cylinders have been replaced (master more than once) about all I add is a few random comments.

Assuming there is no fluid loss and the resevoir remains full maybe the system needs to be pressure bled. I used to wrestle quite a few SAAB systems and they could be a pain in the neck to bleed properly. What I eventually did is use a large thick (1/2") rubber grommet that was large enough to cover the resevoir opening. I glued into place a tire valve stem in the middle of the grommet. I would then use an air line with a regulator on it and apply about 3-4 PSI of air pressure to the system. This would force out any tiny bubbles that might linger and it worked very well.

Another faint possibility could be a master cylinder with a pushrod that is longer than the original. This could cause a condition with no free-play in the clutch pedal and could be half covering a port in the master cylinder.

That’s about my 2 best guesses considering the situation. Wished I had remembered this post as I just got back from your area of CO. Could have taken a look at it while I was there.

Most excellent advice! I would think there may be a small leak somewhere allowing air to be introduced into the system, the trick is to find out where. A minimal amount of fluid replaced by an air bubble seems probable. It could be a pinhole leak somewhere but you have thrown enough money at the most probable parts and it is time to start looking at the others. Are you having even a minimal loss of brake fluid?

Get your mechanic to check the master cylinder to slave cylinder hydraulic line a small hairline crack in the pipe flare can cause problems particularly if it’s a double flare. I have heard of cases where such a fracture doesn’t leak noticeably since the fracture was closed by hydraulic line compression under load but will allow air into the system as the pedal is raised - the now not compressed fracture allows air into the system. You might be better off just replacing it.

Is the reservoir losing fluid? Does it remain full despite the loss of pedal?

Hi, this is Pete here, and I just wanted to add my one last post, with thanks to all who made some suggestions.
On my Cherokee’s “final” trip back to the shop, they took things apart and checked everything over again, and that time they did find a small leak that they’d missed before, it was somewhere on the slave cylinder (which had been replaced once), in a place where the leak was kind of hidden I guess, and no, it was not enough of a leak to noticably drop the fluid level in the reservoir, but I guess enough to lose pressure in the system. Anyway, they replaced it, and now (since the beginning of Feb.) the clutch really has been fine–drove the Jeep over 2000 miles (Denver to Tucson & back). So it was the kind of leak that folks here had been suggesting; thanks again,
Pete, with his Jeep’s clutch actually working right at last (over 260,000 miles now).