Eagle

You "reset" the ECM? The Renix ECU doesn't need to be "reset" -- it resets itself every time you turn off the ignition. I think you have a radiator problem.

You still have the smooth shank where the shock mounts. I'm not a welder, but I think a good welder could weld a new threaded portion onto what's left and you'd be good to go.

Probably 3.73 if it was a 2.8L, maybe even 4.56 if it was a 4-cylinder.

Comanche rear flares are NOT the same as 2-door Cherokee rear flares. The Comanche wheel arch is longer and higher. Cherokee rear flares WILL NOT fit a Comanche. This thread is not about aftermarket flares, it's about OEM replacements. OEM Cherokee flares are one piece, regardless of whether it's a 2-door or a 4-door.

My 87-90 parts manual shows P/N T300 1235 for the MJ. And I don't see any listing for the MJ in the 91-93 parts manual.

^^^ What he said. It is, after all, a load (or height) sensing device. Load pushes the body/chassis closer to the axle, and the valve adjusts to provide more braking. Move the body/chassis away from the axle, and you should expect less braking.

From where? From the overflow bottle? To suck it requires a vacuum -- you can't have a vacuum with the radiator cap off. And it doesn't suck coolant from the bottle into the radiator when you increase the RPM. The radiator is supposed to be full. Coolant expands when it gets hot, so as it heats up some coolant is forced out the filler neck and into the overflow bottle. After you shut the engine off, as the system cools off, the coolant contracts and pulls the overflow back from the catch bottle into the radiator.

All XJs have the same wheel base, so I'm sure the 2-door and 4-door "frame" members are pretty much the same. Somebody did a really neat job getting the floor pans off that shell. They must have spent a week just drilling out spot welds

I pulled that much weight behind a shortbed MJ -- that's why I don't recommend it. The biggest issue IMHO (beyond the brakes, but I assume a trailer for that kind of weight will have trailer brakes) is that the MJ is much lighter in the back than an XJ, so there's much more likelihood of the tail wagging the dog.

It's a tempting idea. The '97 and newer XJ hatches are steel, so a couple of those might be suitable for making a new rear hatch at the back seat, and a second one for the tailgate. But it leaves very little space for actually carrying anything. The only 4-door MJ conversion I've seen photos of is a long bed, and it's like an ocean liner. I think done with a short bed box it would be a nice conversion, and pretty close to what I'd like to own. Unfortunately, I don't have the fab skills to undertake it, nor do I have a shop to play in.

Tongue weight? 3,000 pounds is getting close to the curb weight of an unloaded MJ. 5 miles on local roads should be no problem. 30 miles, especially if on highways, less recommended.

That looks pretty ratty, Don. Aren't you going to have it chrome plated before you install it?

Yes, the shuttle valve is two pieces. In the photo, just to the right of the plunger for the brake warning light switch there's a shoulder, and the last O-ring is just to the right of the shoulder. The basic body ends at that shoulder, and the slider portion is the part to the left, incorporating the recess that the switch plunger rides in. If the front circuit fails, the pressure in the rear circuit pushes the sliding plunger to the right. This pushes up the switch plunger, activating the brake warning light, and it also moves the left-most O-ring to the right to open up the by-pass circuit for full pressure to the rear brakes. Since you have a ZJ proportioning valve, I'd say try it. If you're not getting enough force to the rear brakes, open it up, remove the rubber cup washer and spring inside, and slide the internal plunger all the way toward the nose, then reassemble. Before you install it, open up the big fitting at the nose, and clean out the interior very well. Be sure the rubber cup washer is soft and pliable, and that the plunger can plunge. The XJs have a known issue of eventually losing rear brakes because the proportioning valve clogs up and stops allowing any fluid pressure to the rear. The accepted "fix" in the early days of NAXJA was to remove the cup washer and spring, slide the plunger fully forward, and reassemble. What that did was to eliminate the proportioning function and let the rear brakes have 100% force at all times.

What he said.

Don, you can't use the lower forward outlet from the distribution block. That port doesn't get any brake pressure unless the front brakes fail and the shuttle valve moves to open the inlet to that circuit. That lower port is strictly an emergency bypass. That's why in our back-channel communication I told you you might have to buy a longer flex hose. You have to feed the rear brakes from the "snout" outlet. The other option would be to use an XJ or ZJ proportioning valve, which doesn't have a "snout" outlet and will connect the regular line to the rear to the lower front outlet. MJ Distribution block:

Not really. I tried to cut them close to the centerline, but I wanted to be far enough off the center that I would screw fittings in and still have them stay there. One of them (I think the MJ unit) was done on a metal-cutting band saw in a friend's machine shop. The other one (probably the XJ unit) was done with a hack saw in a vise. If I can find my box of take-out units, I'll see if I can drop the same size drill bits into both (**IF** I have a spare MJ unit that's intact. I know I have several XJ units.)

Duplicate threads merged.

I don't think there's any difference in orifice/passage size between the XJ and MJ valves/blocks/whatchacallems. XJ: MJ:

Okay -- and now you have no brake system warning light. While I am well aware that anyone with half a brain should know if they've lost the front or rear brakes, I don't think it's legal to remove that feature from a vehicle that's registered and driven on public roads. And it doesn't gain you anything -- the MJ block that you eliminated doesn't have any proportioning function, so it's basically doing the same thing as the tee you installed.

Here's my understanding on the XJ vs. ZJ proportioning valve issue: XJ rear brakes are drums. All modern (since about 1930, I think) drum brakes are what used to be referred to as "servo-assisted" brakes. This was so well-known that they stopped using the term long before drum brakes were phased out in favor of disc brakes, but AMC still used the term in their factory service manuals back in the 1960s. What the term means is that the geometry of the shoes and hold-down hardware is such that when the brakes are applied when the vehicle is rolling forward, the rotation of the drums tends to grab the shoes and rotate them against a cam block or pin of some kind to wedge the shoe tighter against the drum, thereby increasing the braking force with no increase in peddle pressure. This is why with drum brakes the parking brake always holds better when the vehicle is pointing downhill (forward) than when it's facing uphill (when the tendency is to roll backward). The reason for a proportioning valve in a front disc/rear drum setup is to limit the braking to the rear wheels in order to compensate for the fact that disc brakes don't (can't) have any servo-assist function. Some vehicles have more of a problem in this regard than others. I've commented previously that the 1968 - 1970 Javelins were front disc/drum rear and did not have a proportioning valve. The 1968-1970 2-seat AMX, which was the exact same car but a foot shorter, DID use a rear proportioning valve. The reason was that the shorter wheelbase made the AMX easier to spin out if the rear brakes locked prematurely. I don't know of any way to document it, but I have read that the ZJ proportioning valve provides LESS proportioning (i.e. more braking) to the rear wheels than the XJ unit. This is because the ZJ has 4-wheel disc brakes and doesn't have any "servo-assist" at the rear wheels. Staying with the MJ unit is just taking it a step farther by not having ANY proportioning. That said, I assume there is already some "proportioning" built into the system, based on the relative sizes of the front and rear rotors and the size of the pads and caliper pistons. I drove my '88 MJ with rear drums and no proportioning for several years before it took itself off the road. Except for one incident that was a result of a combination of circumstances, it was not a problem. I can't know, but I don't think it would have been any different with disc brakes in the rear. And, of course, if it becomes a problem it's relatively easy to plumb in a Wilwood adjustable proportioning valve and fine tune the system. Related reading assignment for the day: https://www.quora.com/Which-one-is-best-drum-brake-or-disc-brake

10-4 ... 1/2x20

True, but you know what happens to your brakes when a line breaks w/o a proportioning valve. They disappear... :???: No, they don't. Both the XJ/ZJ proportioning valve and the MJ distribution block have completely separate circuits for the front and rear brakes. If a front line or hose breaks, you will still have rear brakes. With the MJ unit, you'll have 100% rear brakes, with the XJ/ZJ unit you'll theoretically have 100% rear brakes but more likely you'll have proportioned rear brakes. If a rear line or hose breaks, you'll have 100% front brakes (which you always have, anyway).

With what size engine? If it was off a 6-cylinder it's probably too big for a 2.5L.

The Carter YFA that I'm familiar with is a computer-controlled carburetor that was used by AMC -- I think it's what they used on the '84 and '85 2.5L engines. If that's what you have -- forget it and buy a real carburetor. If you have an older-non-computer version, it may be okay.

Comanchecrusher has a new thread going, on carburetors, so this thread is closed. Otherwise we'll all be talking in circles.