Last Straw: Change Clutch MS or SC

Last Straw: Change Clutch MC or SC

Thanks in advance for help so far in helping me narrow down my two-week clutch system disaster. '93 4.0.

Here's the deal:
- changed MS twice, both new lifetime warranty aftermarket parts
- new clutch kit, aftermarket
- bled about a gallon of fluid, gravity and pumping - not pressure bled

Basically, I get brief normal operation after bleeding and then with some driving am almost twisting my ankle trying to get enough pedal to shift. Note: Normal operation also after sitting all night and in parking garage during work all day. Again, the condition deteriorates with driving.

Should I:

a. change out MS, again, this time with JEEP oem MC for $234?
b. take the trans out and have a look at SC?

Thanks for any advice and could anyone take a crack at explaining in scientific terms or otherwise, why I get normal operation after bleeding nad sitting idle for hours and then consistent return to NO pedal after some driving?

What will cause that sort of pattern?

Unless you're leaking fluid, and assuming your new MC and SC are good, sure sounds like a bleeding problem.
Is your SC external or within the clutch housing? What's been your bleeding procedure?

EDIT: Also, it may be dragging for a different reason, like bad pilot bearing or contaminated disk/plate. Any noise or vibration?

When my Clutch MS was on its way out, it would continue to lose pedal when in heavy stop and go and traffic. It leaks buy the plunger. Recovery was much quicker than over night.

You did not mention what you replaced. Pressure Plate, Clutch Disk, and Slave Cylinder?

Re: Last Straw: Change Clutch MC or SC

Bleeding has been gravity once, just letting it flow and keeping the master full. Mainly bleeding with a hose in the jar, looking for air bubbles with someone working the pedal. I've never failed at this bleeding thing.

There is no noise, no vibration. No chatter. No shake. No slipping. Only this eratic problem with release. Pilot bushing is okay.

the slave cylinders are notorious for leaking. did you change it when you did the clutch. i know the factory parts cost more but they are of better quality. and that could be worth it rather than removing a trans again. did you notice some oily residue in the bell housing? thats a sign of the SC leaking.

There are lots of problems bleeding the internal slave cylinders. Gravity bleed is not reliable. I have done multiple units and I use a electric vacuum operated bleed system. I would take it to someplace that does brakes and have them use a vacuum bleeder like a Snap-On. The wimpy hand pump units are better than nothing, but still fall short. A good vacuum bleeder causes a drop in pressure, making the bubbles expand. That coupled with the much more rapid flow, causes the bubbles to be swept out of the system. I made my unit from a medical vacuum pump and a mason jar.

Brian- did you ever check the hardline going from the MC to the slave? The 89/91 renix years have a hardline that converts to a softline about where the exhaust manifold sits (dunno post `91)- "sometimes" the softline gets wee little holes in it, swells up, leaks,breaks,ect....i tried to get a recall on it, but never had enough support.

*if* that line is leaking even the smallist amount, it`ll suck just enough air inside when it gets used to mess stuff up-but will act like it works fine when it cools off-very small amounts will do it, but its cumulative- the longer you work it, the worse it`ll get over time.

Also how close is it to the exhaust, could be almost boiling once the engine warms up...

It's at the Dealer Now - Last Resort

A trans shop yesterday couldn't fix it. Their solution was tear the whole thing apart. I declined and took it to the Jeep dealer. My service rep there says they have been successful with these difficult bleed jobs. We'll see.

I have no indication of fluid loss. And remember, this began with the clutch replacement. All parts replaced new, Slave, Master everything, but of course the lines. I agree that plastic line seems like a joke. I have been down there when hot though recently and those lines weren't terribly hot.

Up until I pulled the system apart two weeks ago to replace the PP and disc, there were NO pedal/release problems. After two replacement MCs and my guess now is that the original was probably still good, I'm going with air still in the system. There should be some sort of chemical I could run through there that would affect the air in some way and get it to move out with the fluid.