Heat shields / clutch slave

[Orville]

Hi all

I have a 2004 KJ, 3.7l, manual transmission, with about 160k miles. I've recently developed what seems to be a dragging clutch which, if confirmed, would be only 8k miles after a new clutch and clutch slave.

(That's not the first replacement for either -- it's a long and sad story. FWIW, in the most recent case, I went on an unusually high RPM / hilly drive, then there was a brief burning smell while driving, then it wouldn't go into gear when stopped at the next light. The clutch feel and bite point are still normal. It engages gear fine with any forward speed, but sometimes not while stationary and especially after driving it hard. The level of fluid in the master reservoir looks good.)

I was trying to think of reasons why clutch stuff might keep breaking so frequently. It occurred to me that there is nothing between the external clutch slave and the driver side cat, and they're really close together. If the cat is running at 1200F and DOT3 boils at 400F, it would almost be surprising if that didn't cause problems.

My question is: is there supposed to be a heat shield protecting the clutch slave? I don't have another manual liberty to look under and I can't remember whether there used to be one. It's *very* believable that if there was one but it was in poor shape, some highly qualified mechanic decided to throw it away. I can't find any reference in the manual, but they don't always cover stuff like that.

(Apologies if this is a red herring -- trying to think of everything before dropping $$ on yet another clutch.)

 

[adamkrz]

I don't see one under mine,I also have a 04 5 speed, I believe the aftermarket slave cylinders are built cheap.

 

[Orville]

Thanks for taking a look! Just swapped it out for a new one, the least cheap-looking I could find, which seems to be an aluminum body rather than plastic -- not sure whether that's more likely to last or will just absorb more heat -- but either way, fingers crossed it fixes the problem and lasts longer than the last one.

 

[KJowner]

A plastic slave cylinder! Is there anything the Chinese can't make cheaper and worse?

 

[Orville]

In fairness to the plastic slave cylinder, it probably contains metal on the inside, and replacing it didn't solve my problem, so I guess it was working fine after all. Though, there used to be a weird creaking sound when you pushed the clutch pedal which is now largely gone, so maybe I can convince myself the time and the $40 was still worth spending ¯\_(ツ)_/¯.

 

[klc]

Jeep slave cylinders don’t last long. I had to have it replaced three times in twelve years on the old XJ.

 

[KJowner]

If you pump the peddle a few times is it better? Might be the master cylinder instead.

 

[Orville]

@KJowner no, it doesn't seem to help. Also the bite point is still very high even when it's dragging -- as in, you still have to bring your foot almost all the way up to get any bite. So, the hydraulics *feel* pretty strong. I drove with a failing slave once, and I've driven it with air bubbles because it had been badly bled, and that felt completely different -- the hydraulics feel normal to me now.

I also tried warming it up so it drags, then squirting 2 pints of water on the clutch master to cool it down -- if the dragging stops maybe that proves it's the master. Didn't seem to do anything. Although, it's pretty awkward to aim the water all the way back there so I might try that again.

I'm leaning heavily at this point that the pressure plate is somehow heat-damaged or defective, or the pilot bearing is bad. Certainly when it gets warm I still hear creaking noises coming from the bellhousing when I operate the clutch (engine off) which I think are from the pressure plate springs (I thought the noises went away but apparently it's also a hot/cold thing). Like I said, less than 10k miles on the clutch kit, but foolishly I don't actually know what brand clutch kit was used so it might be junk.

I guess it would be logical to do the cheaper master replacement first and then pay money for a clutch job if necessary, but it almost feels like a waste of time (and another $50). If anyone has any thoughts I'd be grateful to hear them.

Thanks for all the advice!

 

[DadOSix]

In the old days, before hydraulics, there was a threaded rod that allowed adjustment of free play. Your issue seems to be in that area. Does the slave bolt only 1 way? No adjustment?

Ive not seen a manual kj but did plenty of work on other breeds with manual

 

[Orville]

There's no adjustment at the pedal or the slave on these manual KJ's. I guess you could bolt the slave on with 180 degree rotation but it seems symmetrical as far as I can tell.

I don't know which direction I would *want* to adjust it. If (say) I put a spacer at the slave, the bite point would be lower to the floor, but then the push rod would go in less far when fully extended so you'd expect the clutch to drag *more* as it wouldn't fully disengage. If I could somehow make the push rod longer, the bite point would be so high I'd be worried that it wasn't fully *engaging* and would start to slip. (The high bite point isn't part of the problem -- it's always been that way -- I just mention it to show that the hydraulics still feel pretty strong.)

Since the clutch works just fine when cold, just drags when hot, in theory (?) I guess that means the adjustment (if it were adjustable) would be about right anyway.

 

[Orville]

For the benefit of any future historians who find this thread, I took it to a transmission shop who said there was significant internal damage to the transmission -- shift rods, synchros and gears -- and to change the clutch while they were at it. So -- wisely or otherwise -- I had it rebuilt. They couldn't suggest *why* the transmission had failed prematurely, except perhaps that it was badly rebuilt when I bought it, so I'm a little concerned they might find their 20k mile warrantee ends up being used if there's still an underlying issue (although I still have no idea what that would be).

The original problems are gone post rebuild. I can't say it shifts great though. I have a suspicion the shifter tower (aftermarket short throw) wore out at the same rate as the internals and is now snagging on all the corners, but can't be sure about that. Maybe it'll "wear in", in a good way...