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Clutch diagnosis


NAXJA Forum User
Hey guys, I've just bought a 1997 manual, and I've got some clutch issues.

The transmission works fine, but the clutch is very spongy. I can push it to the floor with ease, and there isn't much travel in the pedal for clutch engagement. Also, when I first start up, I can hear a very slight grinding noise. If I put my hand on the shifter, and pull it side to side, I can feel that noise as vibration. Its very slight, and I've had to drive the Jeep short distances, so I've just gone with it out of necessity. Because of that, I've also noticed that when the Jeep is good and warmed up, both the noise and vibration go away, but the clutch doesn't get any better.

  • Is the clutch bad? Maybe, but it doesn't slip at all, even in the higher gears. I drove it 75mph in 5th for a little ways, and it was solid.
  • Are the cylinders leaking? Not that I can tell. I don't see anything leaking that looks like dot3, but I also haven't pulled off the factory skip plate yet.
  • Is the fluid low? I don't think so. I opened up the master cylinder, and there's no fill line inside, just a little rubber nipple looking thing. The fluid is filled to maybe just over an inch below the very top of that reservoir. Its a little dirty, but its there.
So I need a sanity check. Slave cylinder is bad maybe? Clutch doesn't fully disengage? Air in the lines? I don't have a lot of manual trans experience. What should I look at next?
Do you ever have to add fluid to the reservoir? Not familiar with the 97 but on many of those reservoirs the rubber nipple-looking thing actually telescopes down to the fluid level to prevent splashing and aeration when the fluid is bounced around.
Sounds like you have air in the system. Usually from a seeping slave cylinder. But it can also happen when the reservoir runs dry. A thought to always have in mind is air leaks much easier than any fluid. Could be a few drop seep that sucks much more air than you'd think.
Just some ideas, not a definitive answer.
I've considered that it may be the slave cylinder. Any tricks to get air out of the system? I think I've read there's a bleeder valve underneath.

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I would start by trying to bleed the clutch. IIRC that can be done by compressing the slave end of the system. Fortunately you should have an external slave. Much easier to service than an internal slave.

If the bleeding of the slave cylinder doesn't make an immediate/remarkable difference then I would suspect the throwout bearing. If the bleeding does make a difference I would then pay attention to how long that difference lasts. Might be good for years, or might only be good for a day or so. That will tell you whether or not you need to change that system. The alternate situation (throwout bearing) wouild be the consequence of the cheap piece of garbage throwout bearing that comes with a clutch kit. The rest of your clutch could be perfectly fine, but that cheap excuse for a bearing can ruin your day. Unfortunately, in order to change it you must pull the transmission.

One other thought: Check the clutch pedal itself. I don't know about '97+ pedal assemblies, but '96 and down are prone to a weld failure/cracking situation. See this thread for some information on that front: https://www.naxja.org/forum/showthread.php?p=246535117
All you have to do to bleed the clutch is make sure you have enough fluid in the master.
Then there is an allen head set screw on top of your slave cyl.
Loosen that up a bit so fluid starts to drain out of it. Close it up, and make sure you have enough fluid in the master.
Repeat a couple times.
I think it would be a good idea to check all the fluids and their conditions while you're at it.
Who knows what you'll find.

You might be able to get by filling the clutch master cylinder with fresh fluid and then pumping the clutch pedal about 50 times. Ten walk away for 15 minutes. Then try it.