Leaking Clutch Internal Slave Cylinder, Motor Mounts to Blame?

[Heavy Metal]

The internal slave cylinder on my 1990 MJ SporTruck (AX15?) 5 speed manual is leaking. After I got home from a ~70 mile trip I was checking my fluids and I noticed that the master reservoir was empty (it is surprising that I made it back with no issues actually). Immediately I checked for leaks from the master in the engine compartment, and inside the cab near the fuse box, there was no sign of leakage. Additionally the line from the master to the slave is fine, however there is evidence of leakage at the mouth of the bell housing.

 

Interestingly, it only seems to leak when the truck is running, I confirmed this by filling the reservoir and letting the truck idle in neutral for a minute, and to my disappointment, watching a steady drip from the bell housing. I shut the truck off and the leak subsided. 

 

Here is what is most disturbing. The day before this trip, I replaced both of my engine mounts (4.0L L6), using a small floor jack to support the motor at the oil pan while I removed and replaced one mount at a time. I am skeptical of coincidences, so it seems to me that I may have damaged the internal slave somehow during the motor mount replacement. Does this seem plausible? My driver's side mount was split about halfway up from tension due to motor torque, and both were noticeably collapsed from bearing the motor's weight. Is it possible that by the new motor mounts changed the angle of the flywheel-to-clutch interface enough to bust my slave cylinder seal? Judging by the fact that it is only leaking while the truck is running I assume it is the seal that is damaged, otherwise it would probably leak when it was off as well right? 

 

Coincidence or not, I am going to bleed it a few times tomorrow in a desperate attempt to see if it sorts itself out so I don't have to drop the transmission!

[Eagle]

Does this seem plausible?

Nope.

[Jeep Driver]

The internal slave cylinder on my 1990 MJ SporTruck (AX15?) 5 speed manual is leaking. After I got home from a ~70 mile trip I was checking my fluids and I noticed that the master reservoir was empty (it is surprising that I made it back with no issues actually). Immediately I checked for leaks from the master in the engine compartment, and inside the cab near the fuse box, there was no sign of leakage. Additionally the line from the master to the slave is fine, however there is evidence of leakage at the mouth of the bell housing.

 

Interestingly, it only seems to leak when the truck is running, I confirmed this by filling the reservoir and letting the truck idle in neutral for a minute, and to my disappointment, watching a steady drip from the bell housing. I shut the truck off and the leak subsided. 

 

Here is what is most disturbing. The day before this trip, I replaced both of my engine mounts (4.0L L6), using a small floor jack to support the motor at the oil pan while I removed and replaced one mount at a time. I am skeptical of coincidences, so it seems to me that I may have damaged the internal slave somehow during the motor mount replacement. Does this seem plausible? My driver's side mount was split about halfway up from tension due to motor torque, and both were noticeably collapsed from bearing the motor's weight. Is it possible that by the new motor mounts changed the angle of the flywheel-to-clutch interface enough to bust my slave cylinder seal? Judging by the fact that it is only leaking while the truck is running I assume it is the seal that is damaged, otherwise it would probably leak when it was off as well right? 

 

Coincidence or not, I am going to bleed it a few times tomorrow in a desperate attempt to see if it sorts itself out so I don't have to drop the transmission!

 

 

 

No need to be desperate. It won't, and you will.

[87MJTIM]

I doubt your changing the motor mounts damaged the slave cylinder.  The internal slave are prone to failure.  Like Jeep Drive said, you are going to drop the trans and change the SC.

 

You may want to find a bell housing from a 94+ AX15 (or the whole trans).  These came with external SC.  These are less prone to failure.

[yxmj]

Is it possible that by the new motor mounts changed the angle of the flywheel-to-clutch interface enough to bust my slave cylinder seal?

 

Think about that for a second....the trans is bolted to the motor....it does not pivot at that point....changing the mounts would have no effect on that junction

 

Interestingly, it only seems to leak when the truck is running, I confirmed this by filling the reservoir and letting the truck idle in neutral for a minute, and to my disappointment, watching a steady drip from the bell housing. I shut the truck off and the leak subsided. 

 

The internal slave has by design has an integral release bearing so when the truck is running it is always rotating....it could be leaking from here or just the vibration caused by this makes it leak it another point .....my guess would be the O-ring coupler at the intake line.

 

You may want to find a bell housing from a 94+ AX15 (or the whole trans).  These came with external SC.  These are less prone to failure.

 

With all do respect .....I do not think the advantage is "less prone to failure".....the advantage is that you do not have to pull the driveshaft/transfer case(if 4x4)/transmission, to change it...with the external it is just a matter of removing 2 bolts on the side of the bellhousing and it is out.

 

It is after all a 25 year old part that get used extensively.....it wore out.......I changes my 28 year old one for a nice cast one i got on e-bay and have had no problems. :thumbsup: 

[Jeep Driver]

With all do respect .....I do not think the advantage is "less prone to failure".....the advantage is that you do not have to pull the driveshaft/transfer case(if 4x4)/transmission, to change it...with the external it is just a matter of removing 2 bolts on the side of the bellhousing and it is out.

 

 

 

New aftermarket are JUNK.

 

It's a stupid design anyway.

[Heavy Metal]

yxmj, I believe you are correct and it is leaking from the o-ring coupler on the hydraulic line into the cylinder. I got under the truck and pulled gently on the bit of hard-line that runs into the bell housing and was able to get it to leak when the truck was not running. I noticed that the hard-line had been resting against the underside of the body, there was evidence of chafing on the undercoating, this must have transferred vibrations directly right to that old and tired o-ring and hastened its demise. 

 

Well, I guess I am going to track down a transmission jack to rent/borrow. I think I have a handle on all the steps to pull the transmission, I am worried about reaching the two transmission-to-motor bolts hidden way at the top of the bell housing. I can't see them right now and from what I have read, they may be external (male?) torx head bolts? Is this likely for the 4.0 and AX15? I have been reading that they are E-12 size, that sound about right? Hopefully the new motor mounts are flexible enough to let me lower the transmission a bit to expose them.

[yxmj]

Look on page 3 of this section there is a thread called "top 2 Transmission bolts"......it will answer your questions

 

The only thing that i would add is as mentioned in the thread loosen the 2 top ones first.......I personally tossed them and replaced them with conventional bolts.