Eagle

The most common cause of this is deterioration of the vacuum line(s) to the football (or softball) where they pass beneath the battery tray. It is definitely caused by a vacuum leak. "All" you have to do is find it.

XJ rear springs are totally different from MJ rear springs. Different length, different arch, different capacity.

That's a good price for that bumper. I've never seen anything nearly that nice for the MJ.

Generation gap, Cruiser. Most (if not all) you guys are too young to remember when cars all came with "three on the tree" -- a 3-speed manual transmission, shifter on the steering column, with no overdrive. The engine that became the Jeep 4.0L was introduced by AMC in 1964 as a 232 cubic inch (3.8L) carburetted engine that was, at the time, fairly revolutionary. In 1966 AMC followed with a de-stroked version displacing 199 cubic inches. The factory axle ratio was 3.08. On the standard tires, the final drive ratio worked out to 24 MPH per 1,000 RPM. That's also what my 1968 Javelin V8 had for a final drive ratio. That happened to equate to exactly 2500 RPM at 60 MPH. 3000 RPM was 72 MPH, and both the sixes and the V8s would cruise happily at 3200 RPM all day long. Redline for both engines was 5,000 RPM -- most wouldn't go much over that anyway because of valve float, but heavy duty, dual-coil valve springs took care of that. 3,000 RPM is definitely NOT "spinning her too fast." It's not even working hard yet. That's right where the engine was originally designed to run.

Does the lower radiator hose have a spring in it? If not, the hose may start to collapse at high RPM when hot, which reduces the coolant flow.

The stock 1988 4.0L cooling system is the closed system. The plastic bottle on the firewall is not an overflow catch tank, it's an integral part of the pressurized cooling system. The bottle should not be filled more than halfway when cold -- there's a post inside the bottle, under the cap, to show you the coolant fill level. Coolant expands as it heats up, so the system needs the air space in the bottle to accommodate the expansion. But there shouldn't be any bubbling. That could be an indication of air in the system.

Personally, I'm of the opinion that updates on your condition and progress are highly relevant to this forum. And, with that in mind, I would suggest (as I'm sure you know) that stress and long hours are probably not an ideal combination for you. If a job switch isn't in the cards, you might consider hitting up your employer with a request for an accommodation under the Americans with Disabilities Act. The accommodation requested would be normal hours, for example. The good thing about that is that, once you mention the ADA, they can't really fire you without leaving themselves wide open to a federal lawsuit over discrimination. Employers are required to make reasonable accommodation for conditions under the ADA.

Unless you have converted to an "open" cooling system, you don't have a coolant overflow tank. How full do you fill that tank?

Do one side at a time. The star wheel adjusters are different for the left and right side. If you get them mixed up, the self-adjusters (which don't work all that well anyway) won't work at all. And take your drums to a shop and have the ridge inside machined off.

I would look for a wiring harness from an '89 or '90 Cherokee. Yes, the tail light and brake light wiring is different in the MJ, but with the electrical manual that's an easy adaptation.

Sorry, I don't know. I'm pretty certain I stumbled across it once, many years ago, but I certainly don't remember page numbers.

ECU?

I never knew there were more than one.

You are not having similar issues. The turn indicator is not in any way related to the brake system warning light. The usual cause of flakey turn indicators on the dashboard is the front turn signal sockets losing their ground, and trying to find a ground path by back-feeding through the indicator light on the cluster. Check your front turn sockets and the grounds for the front lights in general. Going forward, it's better to start your own threads rather than hijack someone else's thread on a different topic. That just creates confusion.

No, it's not. If the brakes were worked on recently, whoever did the work could have tripped the shuttle valve in the distribution block while bleeding, and not known enough to re-set it.

UP? Do they use salt on the roads up there? If so, check ALL the brake lines (or have them checked by a mechanic, on a lift) very carefully. MJs do not like road salt, and the brake lines often fail as they age. A frequent point of failure is where the rear brake lines (there are two) pass over the gas tank. If the brake lines look good -- have a shop or a trusted mechanic bleed the brakes to get the old fluid flushed out. Brake fluid is hygroscopic -- it attracts water vapor, which condenses in the brake lines and collects at low points, allowing the lines to rust from the inside out. I prefer to use silicone brake fluid. It's much more expensive than conventional brake fluid, but it's NOT hygroscopic, so it doesn't have the problem of getting moisture (and water) in the lines.

As Eaglescout526 posted, have to tried rotating the headlight knob? The dash lights are on a rheostat -- they can be dimmed all the way to full OFF by turning the knob.

Welcome to the inner sanctum. When your grandson gets the truck, I hope he will join us, and learn to appreciate the Comanche as a unique and rare vehicle as well as a significant memento of his grandfather. The factory recommendation was 10W30 or 10W40. I run Castrol Syntec 10W40 and change the oil and filter at 5,000 miles. My 1988 Cherokee has survived to 287,000 miles on that, so I see no reason to change. If you are in a VERY cold climate (such as northern New England or Montana/North Dakota), you might consider 5W30 or 5W40 for the winter months, just to get easier starting and faster oiling when cold. Definitely drain or siphon the old gas out and fill it with fresh fuel. No need for high test -- standard grade is all that's required. The '87 has a knock sensor, so it will control the timing to avoid engine knock/ping.

But the Ford axles are narrower than the stock MJ axle.

Axles are the same but you will need to flip the spring perches.

Definitely. You have the central axle disconnect on the front axle. That's operated by vacuum. There's a multi-tube vacuum harness that operates that, and it happens to be located right under the oil filter. Over time, drips from oil filter changes soften and destroy the connectors, resulting in vacuum leaks.

Fusible links are fuses. I would not try to repair them. Downoad the electrical manual, find out what their rating is, and replace them with new wire and actual fuses.

Check the wires the run along the frame in that area. Look for abraded insulation or broken wires.

On an '89 MJ the fuel filter is mounted to the frame rail, beneath the vehicle on the driver's side. If that's not where you saw smoke, what you saw wasn't the fuel filter.