Eagle

Assuming you still have the OEM plastic surge tank, replacing just the cap is not going to resolve the problem. The tank and cap should always be replaced together.

Keep in mind the difference between "fog" lights and "driving" lights. By Federal (and many states') law, "driving" lights may be on only with the high beams, and MUST shut off automatically when you dip the headlights to low beam. They cannot operate when you only have the parking lights on. "Fog" lights are the opposite. They MUST shut off when you flip the headlights to high beam, but they may operate when you only have the parking lights on. Which means you need a bit more than a toggle switch and a relay to control them properly.

IMHO -- not a chance.

On both my XJ and my MJ I have tried replacing rusted-out sections of brake line, only to have another section explode while trying to bleed the brakes after the repair. Do NOT try to save pennies by using junkyard brake line.

If he got the pinion depth and the backlash within spec, he doesn't have a carrier break issue. If he had the wrong carrier it would be physically impossible to set up within spec.

In your state, are body shops licensed as auto repair shops like dealerships and repair shops? If so, report the shop both to the Better Business Bureau and to the state agency that handles the licensing. If there's no license, you can still report them to the BBB. I think your best bet, especially since you seem to have as many MJs as I do, is to learn to do body work. For a lot less than you paid for that job, you could have purchased a high quality gas/wire welder that would enable you to do your own repairs and know that the rust was repaired with metal.

Do you still have the original cooling system, with the plastic reservoir on the passenger side of the firewall? If so, one possibility (probability, more likely) is that the cap isn't able to hold pressure any more. In the 87 - 90 4.0L cooling system, that bottle is not an overflow recovery bottle. It is a part of the pressurized system, and that cap is a pressure cap. When they get old, being plastic, they lose the ability to seal. The other point is ... how full do you fill that reservoir? There is NO overflow for the "closed" system -- which is why it is nick-named the "closed" system. There has to be air in the system to allow for expansion. If you look into the opening in that reservoir bottle, you'll see a post sticking up. That's how full you should fill it when the system is cold. It fills to the halfway point of the bottle, with the additional volume to allow for when the coolant gets hot and expands. If you've been filling it up to the top -- you've been over-filling it, and stressing the pressure cap in a way it wasn't designed to be stressed. Quadratec used to sell a complete replacement (plastic) bottle for $19, with cap. It's probably a few $$$ more now, but ti's still the cheapest way out. There are other solutions available using high quality aluminum parts, but they're a LOT more money. If you're interested, I'm sure a search will turn up the discussions.

A Grand Cherokee will have the larger shafts (I think), but it's a low pinion, so it's not much of an "upgrade."

It will also require a complete engine wiring harness, and it may involve some alterations to the chassis harness, as well. For example, the V6 has a mechanical fuel pump. You'll have to get power to the tank for the electric fuel pump. Oh, yeah -- you'll need a gas tank and fuel pump.

I agree. That truck is far too nice to scavange parts off for some other rig. I'd keep it, put a fresh coat of paint and some good rust-proofing on it, and use it as a summer daily driver. The 4x4 will get you through the winter, and if it already has some rust then a bit more won't kill it.

The temp sensor and the oil pressure sensor for the gauges would be the same for an 86 as for an 88. That's not the problem. Begin by testing the gauges themselves. You'll need an assistant. For either gauge, the sensors are variable resistors. The range is zero ohms to 88 ohms. Zero ohms, of course, is no resistance, or a short circuit. So, as a rough "go / no go" test, you turn on the ignition (the engine can be running, but be careful where you put your hands. The engine does not NEED to be running, but the ignition has to be on.) Take the wire off one of the sensors. You now have an open circuit ==> infinite resistance. The needle on the gauge should swing all the way to the right. Now find a clean, dry place on the engine block and touch the wire to the block to ground it. You now have zero resistance. The needle on the gauge should swing to the opposite end of the scale. Repeat for the other gauge. If the gauge fails this simple test, you have a faulty gauge, or a break in the wiring between the gauge and the sensor. If you know the idiot lights worked before, the wiring should be good. Problem is, you have no way of knowing whether or not the idiot lights actually worked, because the start-up test only checks the bulb, it can't check the circuit. Let us know what you find.

XJ flares won't work in the rear. They are about 2" too short lengthwise, and about 1-1/2" too short in height. To use XJ flares, you would have to cut out the flare area from a 2-door XJ and graft it onto the MJ to reduce the size of the wheel opening.

I believe I used '95 YJ hoses in the '88 MJ when I had the lift in it, too. Had to re-bend the hard line on the caliper end slightly, but the fittings went together and they were plenty long enough for a 4" lift.

The '96 is a mongrel. That was the first year they went over to OBD-II, and the way they did it was sort of bastardized because it was adapted into the 91-95 chassis harness. The '97+ was an all-new harness. You need a harness from something in the 1991 to 1995 range.

If the backing plate is the same, then the axle length is different. Several years ago I got my hands on a Dana 44 rear axle. It had backing plates, but no drums. "No problem," sez me, "I'll just use the skinny D35 drums until I can afford new D44 drums." Visually, there was definitely more of a "bell" shape to the center web portion of the D35 drums than on a nearby D44 axle. I was sure it would work -- but it didn't. The back (open rim) of the drums bottomed out on the backing plate before the center "hat" made contact with the axle hub. So either the backing plates are different, or the D44 axle shafts are longer (or the D44 axle tubes are shorter -- hadn't considered that possibility before). Something is different, 'cause it didn't work like it was supposed ta.

Under-hood convenience light?

You also have to switch to 16" rims, I believe, because I don't think 15" rims will clear the WJ calipers.

The rear is a whole different can of worms. From 1986 (1984, for the XJ) through 1989 the Dana 35 (most, anyway) had 10" x 1-3/4" drums, and the Dana 44 (most, anyway) had 10" x 2-1/2" drums. And the offset on the backing plates isn't the same, so if you try to upgrade the 1-3/4" drums to 2-1/2" just by buying new drums -- the back/inside flange of the drum bottoms out on the backing plate before the center part of the drum makes contact with the hub on the axle. So to make this change you have to replace everything from the backing plates out. And then in 1990 Chrysler switched from the two 10" drums sizes to 9" x 2-1/2" drums. There's no reason you can't just swap a 90+ rear axle into an older XJ or MJ, or go the other way, but it's another case of then having to remember to buy parts according to the year of the axle rather than the year of the vehicle.

How do you put Explorer rotors on WJ hubs with a different bolt circle? And even if you redrill the rotors to fit on the hubs, the front wheels then have a different bolt circle than the back wheels. And how do you know the rotor offset is the same as the WJ rotors? I'm confused. I know people do WJ front brake conversions, but they don't ignore the bolt circle issue.

You can't run 1991 XJ/MJ hubs with WJ brakes. The MJ has a 5x4.5" bolt circle, the WJ has a 5x5" circle.

Advance Auto, Auto Zone, Pep Boys, Checkers, NAPA, Carquest ...

There are more than two permutations and combinations. http://comancheclub.com/forums/viewtopi ... s&start=15 See my long post on the second page. Capsule summary: ALL parts (hub, rotor, caliper and knuckle) have to come from the same "generation" or you have an interference fit.

A Jeep 4.0L will run 10,000 RPM, too ... if you can get beyond the 6,000 to 6,500 RPM vibration range without self-destructing.

Make certain you remove the throttle position sensor. They don't like to get wet -- which is why yours started running funny after you left the hood open for awhile. I had a mental lapse and left the hood up overnight a couple of weeks ago after doing some minor work. Naturally it rained that night (thankfully not too hard), and the thing ran terrible for most of the next day. Didn't want to idle under 3000 RPM. Then I parked it for a few hours after it had gotten fully warmed up, and I guess the heat baked off whatever moisture had gotten into it. It's been fine ever since.

God, I hope not. No offense, but I simply cannot see any advantage to the buyer in a timing belt that has to be replaced every 80,000 miles compared to a timing chain that goes 300,000 without a whimper. But I know I'm old-fashioned.