AZJeff

NOT TRUE. I have converted several systems that were designed for R12 into operating on R134a. One just has to follow a bunch of special "rules" when doing so. It IS true that some conversions loose some performance, and that the converted vehicle won't get as cold using the AC with the new refrigerant as it did with R12. However, in the case of an MJ, the HVAC system was designed to cool and heat the interior volume of an XJ, so the little cab of the MJ pickup has much less volume, so the system is overdesigned for that application. That means any losses in performance by switching to R134a won't be noticed in an MJ cab. The important major "rules" to follow in the conversion are the following: 1. ALL old refrigerant MUST be removed by vacuuming the system. 2. A new receiver/dryer (accumulator) must be installed. 3. New refrigerant oil that is compatible with R134a must be added to the system. You get a lot of the old oil when you replace the accumulator, and, in the case of the OP, he is replacing his evaporator, so some more old oil comes out with that, too. (The remaining R12-type oil will not circulate with the new R134a, and thus will settle to the low places in the system, mostly in the condenser.) 4. ALL o-rings must be replaced with ones compatible with the R134a 5. The converted system should be charged with LESS refrigerant than what was called for with R12. The rule of thumb is to use a charge of 80 of what was called for my the factory with R12.

Don't bother to "immediately reconnect" the parts of the system. Once the system is opened even for a few seconds, the system is now "contaminated" by air and moisture, and must be evacuated before being refilled. The reason to cover all the openings you create in the refrigerant plumbing is to keep DIRT out, more than anything else.

Which brings up a good question to the OP—are you planning on converting to R134a while you are redoing your AC hardware? This is the BEST time to do so, as you can also flush the condenser to get most of the R12 oil out at this time.

I am assuming you know the cause of why your AC doesn't work and are fixing that as part of the process as well. BTW, if you are not savvy on AC systems, when you replace major components like the evaporator (or whatever), it's good practice to replace the accumulator (aka "receiver/drier") at the same time.

If you are going to open up the heater box to do any repair/restoration on it, I STRONGLY advise you to replace the heater core and the evaporator while it's apart. The parts are not that expensive, but if you choose to save money now, be aware that the labor to change them later means tearing most of the dash back apart again. (The same thing applies to the blower motor assembly.) Actual removal of the heater box is quite straightforward, with a few studs holding the box to the firewall. Of course, the coolant must be drained, and the heater hoses must be disconnected. Likewise, the AC system must be discharged and disconnected to remove the box. When you put it back in, if you do not have access to refrigeration service tools, you can take it to any shop that does have the tools, and tell them what you did. They can then evacuate and recharge the system to restore it's function. You have your MJ in a state right now that rebuilding the heater box would be a no-brainer, and when you are done, you will never have to worry about it again. If you need more tips on the finer points of doing this, I can provide more, as I just did this on my MJ back in November.

Oil pan removal on an MJ/XJ almost ALWAYS requires that the front axle be allowed to "droop" lower than what the factory design specifications allow. This applies even if the vehicle has up to about a 3" lift. Knowing this, here is the best way to get the pan off: 1. Jack the vehicle up until the vehicle is high enough that the front wheels are off the ground when the front shock absorbers are FULLY extended. Support the chassis of the vehicle in this position. 2. Remove the front wheels and place a jack under the axle in the middle of the span. 3. Lift the axle slightly to take the load off the lower shock absorber attaching bolts, and remove those bolts on each side. Let the axle droop lower by about 3 inches. SUPPORT the axle with jack stands in this position. NOTE #1--Be careful not to overstretch the brake caliper hoses when doing this. If they become stretched, remove the caliper from the axle, and hook it to the coil spring to keep the brake hose from being damaged. NOTE #2--The sway bar links (if equipped) may need to be removed from the sway bar temporarily to allow the axle to droop sufficiently in some cases. 4. Remove the starter from the vehicle. Be sure to DISCONNECT THE BATTERY before doing thi. 5. Once the axle is lowered enough and the starter is out, the oil pan bolts can all be removed, and the pan can be dropped and slid rearward out of the vehicle. The bolts that hold the pan to the block are two sizes: the smaller ones attach the pan in all locations except the four "corners" of the pan, where a larger bolt is used in those specific spots.

You can buy headliner material as some fabric/sewing stores. It’s more stretchy than regular fabric, and you might find it in a close match color.

I bought my stuff from Grainger. You can get both open cell and closed cell foam in various thicknesses and then cut to shape with a knife or scissors. The downside is that the stuff is not cheap. But....it does do the job as well as OEM, and since OEM is no longer available, it's about the only solution. I have few pictures of what I did, if I search around for them.

how about a single layer of fiberglass mat bonded to the back side of the existing headliner base material? Not too heavy, but stiff enough.

The term they used to use was "watershield paper" back when those types of things were made from some sort of wax coated butcher paper, around 1000 years ago when I started working on cars. Eagle is probably quoting Jeep's official term for it. When I have ones that tear, etc., I make a new one out of 3-4 mil think polyethylene sheet, and cut it to shape with scissors. The BEST way to attach it to the door is using the method that the factory did, which is a butyl tape. You can get the stuff on Amazon: https://www.amazon.com/Sealant-Headlight-Retrofit-Headlamps-Windshield/dp/B09SF18Y8T/ref=sr_1_4?keywords=butyl%2Btape&qid=1673119896&rnid=2941120011&s=automotive&sr=1-4&th=1

There are TONS if videos on YouTube covering the R&R of the RMS and pan gasket on the 4.0 Often the video shows the job being done on a YJ, TJ, or XJ, but they are the same as the MJ, except for how one goes about getting the oil pan out after it is detached from the engine. My preferred method to getting the pan out is to jack the vehicle up so the front wheels clear the ground, and then place jack stands under the "frame" by the lower control arm pickup points. Then place the jack under front axle, and remove the front wheels. Then lower the front axle down as far as it will go. If that is STILL not enough to get the pan out, then remove the lower shock mounting bolts, and lower the axle a bit more with the jack. Once the pan is out, put some jack stands under the front axle to support it while you do the seal work. Once you are ready to reinstall the pan, take the jack stands out and lower the front axle as needed to get the pan back in.

That’s a new type of plug failure I have NEVER SEEN, either in person or via photo. And I have been working on cars for 55 years. what does the plug hole in the head look like?

I remember seeing a member here who posted a link to someone who makes reproduction underwood decals for Jeep vehicles. I am looking to replace several decals on my 1989 MJ, but has the driveline of a 2000XJ, so I need those XJ specific decals. Does anyone have the link to that vendor?

Yeah, I might sound like I am stating the obvious, but in my years on the XJ forums, I found a ton of owners who complained about belt squeal, only to discover they were not using a belt tension measuring tool, and/or they underestimated the amount of tension actually required. And you are absolutely correct. The older 4.0 tensioning scheme for the XJ and MJ sucked. It was much harder to get sufficient tension than with the later system (which, unfortunately was used only on the later XJ's.)

The 4.0 in the MJ and XJ models is VERY sensitive to lack of proper belt tension. On top of this, they seem to need a hellacious amount of tension compared to some other vehicles. This means that many DIY guys under-tighten the belt, and noise ensues. Add in belt aging, and crud on the belt and/or pulleys, and it can be really annoying.

If you are attempting to restore the dash so it has the same appearance as when it left the factory, “JustDashes.com” (or any of their competitors, if they exist) are your best choices. The OEM construction is foam over a plastic dash structure, and that is covered by a layer of vinyl. Duplicating that without the right fixtures an d materials will be almost impossible.

I put a complete Teraflex kit on my D44, and although its' been a few years, I seem to remember the spacers that Teraflex provided were of an incorrect dimension. I cannot remember for sure, but I seem to think they were too thick. I am going to go check my records to see what instructions I gave the machine shop that altered them for me.

I tried to type in a description into both eBay and some search engines, and I got nothing. If you have a part number, that would help in a search.

Actually, I would like a few (6?). My interior color is redone to match my 2000XJ dash, so I would respray any color I got with the proper Chrysler "Agate" interior paint.

Several of the interior panels of the MJ have screw holes that are covered by a plastic plug to conceal the hole once the panel is installed. When putting in a new heater core recently, I lost one of my hole plugs. Does anyone have a source of replacments? (other than trying to find some in a junkyard) I supposed I could modify (shorten) the conventional hole plugs that can be had from hardware suppliers, but they are not exactly the right diameter, and the modification will be tricky due to the small size.

What you are talking about are "polyurethane" bushings. Polyurethane is much stiffer than regular rubber, when used in bushings. Its commonly used on applications where precision handling is needed (like on race cars or the like.) It is not used on "regular" street vehicles because the polyurethane transmits much more shock and vibration back into the chassis, and can make ride quality quite harsh. Unless you are running the baja in your MJ, I would steer clear of polyurethane.

THANK YOU!!!!

The AC lines that connect to the evaporator have a secondary "safety clip" that surrounds the joint. It's made of sheet metal, and I assume it's intended to insure the line will not slide apart due to pressure of it's own accord. My MJ, which has a 2000 XJ evaporator in it, has that clip on the low pressure (suction) side, but lacks one on the high pressure ("Liquid") side. Can anyone provide the Chrysler part number (or a source) for the clip for the high pressure side clip?

Interesting.....I admit my forays into major brake system repairs were not steady through my years of working on stuff, since I am not a pro and strictly DIY. All I can say is that, over the years, I never saw anything but the almost clear (straw?) colored stuff, and then the cruddy brown/rusty/icky stuff I removed. Good to know about this.....THANKS.

YUP. This is going to be the best way to determine if starting/running the engine any further is going to do any serious damage to what is in there.