Clutch not maintaining pressure when depressed!?!

I have a 91 Jeep Cherokee inline 6 5spd with an internal hydraulic throwout bearing for the slave cylinder for the clutch. I have verified that there is no fluid leak at all. I have tried bleeding the system multiple times. Works good for the first couple minutes driving then fails. The problem is that a person can't hold the clutch down for more than like 20 seconds without the clutch failing to hold pressure and then you can't shift any gears. A quick reapplication of the clutch and then it is fine to shift gears. The throwout bearing was just installed new. After the factory shipping tabs on the bearing were broken the mainline was disconnected once to remove the tranny to replace the worn out clutch disc. Thanks!

P.S. Anyone have any fixes for repairing cracked exhaust headers? Getting a new one is not an option!

Quills said:

I have a 91 Jeep Cherokee inline 6 5spd with an internal hydraulic throwout bearing for the slave cylinder for the clutch. I have verified that there is no fluid leak at all. I have tried bleeding the system multiple times. Works good for the first couple minutes driving then fails. The problem is that a person can't hold the clutch down for more than like 20 seconds without the clutch failing to hold pressure and then you can't shift any gears. A quick reapplication of the clutch and then it is fine to shift gears. The throwout bearing was just installed new. After the factory shipping tabs on the bearing were broken the mainline was disconnected once to remove the tranny to replace the worn out clutch disc. Thanks!

P.S. Anyone have any fixes for repairing cracked exhaust headers? Getting a new one is not an option!

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OK....so you replaced the trowout bearing in the trans, and I'm going to assume that you replaced the internal clutch cylinder while you were there as well. So you've bled it out, and it comes back. I had mine get progressively worse and let it gravity bleed, and it works fine now. This was after about 1 yr since the clutch was originally done. If you've done what you say you have your only other option is the clutch master cylinder, the little thing crammed in the corner by the brake master cylinder.

It sounds like what a master cylinder does when it fails. It is either....

a. Leaking ( CHeck behind the firewall under your dash, as it is detremental to your wiring if it is)...OR

b. The fluid in the system is internally bypassing the seals so that once it does work...it more or less "fades" outwhen the fluid bypasses the internal seals thus not allowing it to hold pressure anymore.

I say change the clutch master. Escpecially if it is a high mile vehicle.

Good Luck.

Since you're sure there are no leaks, and you replaced the slave/throwout, sounds like your master cylinder is shot. They don't always leak fluid when they go bad. Yours just isn't holding pressure. Like red91 says, master cylinder is the only part you haven't replaced. Good luck.

I am going to investigate the master. Is it at all possible that my hydraulic throwout bearing (slave) has an internal leak? The part is brand new so I wouldn't think so, but...

Quills said:

I am going to investigate the master. Is it at all possible that my hydraulic throwout bearing (slave) has an internal leak? The part is brand new so I wouldn't think so, but...

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highly unlikely. not for new...but it could have created enough pressure to have screwed with the master clutch cylinder. Thats why they should be replaced as pairs.

Quills said:

I am going to investigate the master. Is it at all possible that my hydraulic throwout bearing (slave) has an internal leak? The part is brand new so I wouldn't think so, but...

Click to expand...

It's not impossible for the slave to either have a leak or just be a bad part from the outset but if it was leaking, you'd see hydraulic fluid drip out from the bellhousing.
Like the others have said, it's more likely that the clutch master cylinder is shot. I was getting similar symptoms in my Jeep and replacing the master cylinder certainly improved things. Mine cost $40 and took only 30 minutes to replace.
If that doesn't cure the problem, it looks like you'll have to remove the tranny and replace the slave again. I know, it's a big PITA.

Quills, the slave cylinder cannot have an internal leak, like a master cylinder can. The pressurized fluid from the master cylinder pushes on the slave's piston, moving it out. If that piston leaks, the fluid exits the slave, and collects inside the bell housing, then drips to the ground--you'll see it. The master cylinder piston seal can allow the fluid to move passed it, but it has no where to go, accept behind the piston. So you won't see any of the fluid, because it stays inside the master cylinder. It's good practice to replace your master cylinder when you replace your slave/throw-out bearing assembly; you just haven't finished the job.

red91inWA said:

It sounds like what a master cylinder does when it fails. It is either....

a. Leaking ( CHeck behind the firewall under your dash, as it is detremental to your wiring if it is)...

I say change the clutch master. Escpecially if it is a high mile vehicle.

Good Luck.

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I have the exact same problem with my Jeep. I was overseas for a year (Afghanistan vacation courtesy of the US Army National Guard) and my Jeep pretty much just sat there waiting for me to get home. Anyway, I drove it and noticed the smell of something like brake fluid. I had to fill the brake fluid resovoir and I figured that I must have managed to spill some someplace inside. Now, my clutch has just started having the same symptoms descibed above. So, after reading this thread, I went out and looked under the dash and low and behold, the master cylinder is leaking on the inside of the firewall.

I feel like an idiot.

I guess it's time to change the master cylinder.

Now, if I could just find that pesky oil leak...

Thanks for the help!

You could try some thermosteel on the exhaust header....

Or Peratex also makes a compound for repairing headers.

And a reminder, that if you do have brake fluid leaking under the dash, it more than likely has dripped onto the fuse block. It will cause bad connections between the fuses and their respective holders; you will need to clean it with brakleen.

atticus2007 said:

I have the exact same problem with my Jeep. I was overseas for a year (Afghanistan vacation courtesy of the US Army National Guard) and my Jeep pretty much just sat there waiting for me to get home. Anyway, I drove it and noticed the smell of something like brake fluid. I had to fill the brake fluid resovoir and I figured that I must have managed to spill some someplace inside. Now, my clutch has just started having the same symptoms descibed above. So, after reading this thread, I went out and looked under the dash and low and behold, the master cylinder is leaking on the inside of the firewall.

I feel like an idiot.

I guess it's time to change the master cylinder.

Now, if I could just find that pesky oil leak...

Thanks for the help!

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Like he said, get in there with some good electrical cleaner and make sure the fuse block is really clean. Break fluid will eat it!!!
You don't want the XJ the start having a nervous tick.