I have a '92 YJ with the 4.0L, five-speed, 1-inch body lift, and 31-inch tires. It is a commuter vehicle but I love it. The Jeep is going through clutch master cylinders like crazy, they leak at the stem in the cab side of the firewall at the pedal connection. I have tried O'Reilly's, Napa, and Chrysler replacement parts, but what is the trick? Replacing and rebleeding every 8 to 10 months gets real old.
I bought this Jeep two years ago with 200,000 miles on it. I have rebuilt the engine, brakes, transmission, and transfer case. I replaced the clutch and slave when leaking, and sealed it. About all that is left is paint and interior and this thing will be "like" new, but this clutch master cylinder is driving me nuts. I'm on the third one since an engine and trans overhaul maybe 6,000 miles ago. Is there an update or some trick? Let me know, please.
I am not sure if I have a solution or not. I checked for any factory TSBs on the subject and came up with none on the master cylinder. I checked a factory service manual to see if I was missing something that you might have inadvertently done.
I assume that you are not trying to rebuild the master cylinder with some kind of a kit. If so, you're really out of luck as the aluminum cylinder doesn't hone properly. I was also under the impression that one could not just buy the master cylinder from Jeep but had to also buy the slave and the connecting hose, and that is about $200, the last time I looked.
Where you say it is leaking is just about the only place that it can leak any fluid out. My best guess is that the pushrod is not attached to the clutch arm in the proper location. When you depress the clutch, the pushrod may be at too much of an angle and is putting some side load on the piston, causing the cup to not seal properly. Could it be that someone, for some reason or another, changed out the clutch-pedal assembly for something different, or that the Jeep originally had an automatic trans and was converted to a manual and the wrong clutch-pedal assembly was installed?
I suggest you take a close look at the pushrod, and make sure when the clutch pedal is pushed in, the rod pushes straight into the piston and not on an angle. If it does go in on an angle, then I suggest that you redrill the mounting hole on the clutch arm so that it pushes straight in.
I like to look at off-highway vehicles, be it a super-trick rockcrawler or an average trail rig, as there is always something interesting on them. Lots of times I get some really good ideas to pass on to readers of this column. However, this month, I want to pass on some "bad" things that I commonly see.
1 Excessive U-bolt length: Most spring-under-axle vehicles, such as CJs and TJs, have their U-bolts over the top of the axle pointed downward past the springs and through a bottom plate. Nuts are used to tighten the U-bolts to hold the leaf-spring pack up against the axle. The excessive amount of U-bolt length past the nut is not only a great rock catcher, but you take the chance of it actually breaking the U-bolt when it does catch on an obstacle. Cut the excess off! Even at that, you still have the nuts hanging down. There are several aftermarket companies that make skidplates for these nuts, but these reduce ground clearance. Your better choice is some special spring plates with wings off to each side that move the nuts up above the bottom of the spring.
2 No bumpstops or improper-length bumpstops: Bumpstops are there for a number of reasons. They keep steering components such as the tie rod or drag link from contacting the frame; the differential housing or driveshaft from hitting the engine; and, best of all, they act as an extra cushion when the axle reaches its limit of upper travel. One of the fastest ways to destroy a leaf-spring pack is to let a positive arch go into a negative arch. The same thing goes for shocks-they should never bottom out their stroke before a bumpstop is fully compressed. I've actually heard people say something like, "Oh, my springs are so stiff, they never flex that much." Well, I'm glad I'm not riding in that vehicle.