AZJeff

The 4.0 engine has what is called a "controlled crankcase ventilation system". That means that the rear hose is sized such that an engine in "as designed" condition will suck normal amounts of crankcase vapors through that rear hose and burn them with the combustion air being drawn into the intake manifold. When a 4.0 engine becomes substantially worn, this vent hose is not large enough to deal with the larger-than-normal amount of blow-by that the cylinders leak into the crankcase past the piston rings. Once this condition exists, the crankcase now has more pressure in it than the rear vent hose can scavenge from the bottom end of the engine, and the excess vapors now seek another way out. That way out is the front hose on the valve cover, which is normally providing INLET AIR to the crankcase. The end result is oil vapors in the air filter and air box. One can increase the size of the rear crankcase vent hose, but that also upsets the airflow mass being measured by the MAP and Throttle Position Sensor, and will result in a leaner mixture. A little bit of extra crankcase vapors being sucked in by a larger vent hose is not seriously harmful, but a large amount will cause long-term engine damage. (Using a PCV like "Pizzaman09" suggested helps limit the amount of crankcase gases being drawn into the manifold to some degree.) The real fix, of course, is to fix the blow-by on the engine by reboring the engine for oversized pistons/rings.

That cover is used mostly to keep people from kicking the latticework grate on the bottom of the heater box where recirculating air enters. The grate is plastic, and can easily be broken not someone with big feet. It is not essential to operation of anything on the vehicle.

If you search on Amazon, you can find multiple choices there. If you don’t mind paying a bit more, Crutchfield offers a searchable database of their offerings, plus an installation kit that will make installation and hookup much faster, if you lack a wiring diagram and a soldering iron.

JVC and Pioneer both make single DIN radios that fit MJ/XJ dashboards. They offer models that are Bluetooth/USB, and some also have CD capabilities as well.

The purpose of the foam is to seal the recirculation door against the heater housing. It also cushions the door as it moves to that position against the lattice work. You can purchase sheets of “closed cell neoprene foam” of 1/8” thickness on Amazon. It can be attached to that recirculation mode door with spray adhesive. Of course, to do this, you must remove the heater box to remove the door for this repair.

I believe this is correct. I seem to recollect that the trans control subsystem changed when they went to OBD2, and was further refined in the last couple of years of XJ’s.

I am retired, and I know about cash flow. I had a machine shop redo the short block on my MJ, which had budgeted for. However, that interrupted over the past 12 months by unexpected heart surgery due an infected heart valve.😳

Current factory Mopar branded oil drain plugs have a polymer washer that is molded on to the flange head of the drain plug bolt. Dorman makes an equivalent, and is available from Oreilly auto parts. Drain Plug

Fusible links were popular in some brands of domestic vehicles up into the early 1970’s. Apparently AMC did it longer than others, probably due to budget constraints. If I was redoing any power wiring in an older MJ/XJ, I would ditch the fusible links and put in a small fuse panel like show earlier in this thread. It’s easier to diagnose issues and control power distribution with such an improvement, and the cost would relatively low.

its possible that those loose/damaged spindle threads have damaged the existing bearings in ways you cannot see completely. The cost of wheel bearings listed on Rock Auto is so cheap I would just plunk the cash down for all new bearings and seals and remove any doubts about those elements from the equation on any source of the noise.

Yeah, the mounting scheme for the Saginaw steering box in the MJ and XJ is not the best. Aside from the fact they only use three bolts (instead of four found in other Saginaw boxes), they rely on some formed internal sheet metal spacers to keep the two "walls" of the frame from collapsing towards each other when the mounting bolts are tightened. Further complicating the flimsiness of the mounting is that the walls of the frame are not that thick, so getting rambunctious with the wrench when tightening the steering box mounting, one can potentially collapse the frame in the steering box area. The aftermarket steering box spacers help to reinforce this part of the frame, as does the use of large HARDENED washers under the heads of the steering box bolts. (Using longer steerring box mounting bolts allows the use of such washers.) And how do I know this? Because my MJ was wandering on the road, and I found that my frame was cracked around the steering box bolt holes, causing the box to move when the steering wheel was turned. (A previous owner had put some monster swamper tires on the vehicle, and it overstressed the box mounting.) To fix this, I ended up welding in more robust spacers and some gusset plates to fix the cracked frame walls. Since I have performed that repair/upgrade, my steering box has been noise free, solid, and steering is more precise (at least more precise for a solid axle pickup truck with recirculating ball steering.)

The following observation is almost worthy of being posted as a “sticky” on this forum: All of our MJ’s are really pretty old vehicles nowadays. That means any rubber components in the suspension system are really dried out and probably cracked from age and/or heat if they are still original. That means that anytime there are noises in the suspension, or irregular steering behavior, a detailed inspection of parts is warranted. Even more important is that, if anything in the suspension/steering is suspect or “slightly worn”, it probably would be wise to replace that part general principles. BTW, this applies to engine and transmission mounts as well. Those OEM mounts were not the most robust to begin with, and thus can benefit from replacement even if they “seem” OK.

In addition to a visual inspection of steering linkage joints, I find that wrapping your hand around the joint so that you are grasping both halves of the connection is helpful. With this type of grip, you are able to feel the relative motion between the two parts of the joint.

Any welding in the middle of the hood to attach the under structure to the hood skin is going to distort the surface at least minorly, and that would necessitate some secondary work to remove that distortion. Adhesives of any kind will keep the surface skin from “oil canning” against the underlying ribs and making noise.

There are structural adhesives used in the body shop industry that will bond your hood pieces in the center areas quite nicely, and will be mush more effective than the stuff AMC and Chrysler used back when MJs were in production. if you know of a body shop supply store, they would carry this type of stuff. Otherwise, some internet searching is you next best bet.

Pete is on to the best, most reliable solution. Unless you are trying to restore your MJ to “as built” condition, keeping that sliding axle lock claptrap is a PITA. Bypassing (overriding) that mechanism makes the axle behave like all the later XJs (and the TJs) which were problem free in this aspect, and the fuel economy losses were insignificant.

I can see from the photos that the sway bar bushings where the bar attaches to the chassis need replacing. the chassis end of the track bar is junk as well. All the other steering linkage stuff cannot be ascertained without doing the “rock the steering wheel back and forth” test while holding/feeling each joint. Contol arm bushings need a close inspection with a flashlight to look for cracks or permanent deformation. Keep in mind that, unless those arms were replaced or rebushed some time in the past, you are rolling around on 30+ year old rubber suspension joints, and that almost guarantees that the bushings are just flat worn out.

On ALL versions of the MJ or XJ, the rear can be lifted by a Jack on the differential housing (aka “the pumpkin”) and Jack stands placed as shown in th OP diagram on the chassis near the front leaf spring attaching point. For the front of 2wd versions, I would Jack the front tube near the lower control arm attachment points, and place the Jack stands in the locations indicated in the shop manual. I am quite surprised that they caution against using a floor Jack on axle tubes, because I have been doing that on TONS of vehicles for the past 50+ years, including MANY Jeeps, and have never damaged any of them.

Any play in the steering linkage is unacceptable. The parts affected should be replaced.

That’s who I use. (My wife, not yours.)

One of the best ways to check for steering system looseness is to have a helper sit in the vehicle with the engine off and rock the unlocked steering wheel side to side until they feel the force to turn the wheel get high. This essentially takes all the lash out of the steering system. while the guy in the cab is doing that activity, you climb underneath and check each joint one at a time. The way you check the joint is both visual and by feel. the “by feel” part involves grasping the individual joint by hand, trying to encircle both halves of that steering linkage connection with your hand and fingers. You are attempting to feel for any relative play between the two parts of that particular steering linkage connection. this test only works on the steering linkage and on the track bar connections. The test for control arm looseness is only really feasible with a BRIGHT flashlight and visual inspection, looking for cracks in the rubber and/or permanent rubber deformation.

Steering stabilizers DO NOT remove vibrations. They merely reduce them. Pete M raises some good questions about/where the vibrations are felt. Based on the speed you stated, it sure sounds like a tire balance issue, but answering Pete’s questions will give some clues as to the source.

I already tried Wrangler knobs. They are significantly smaller in diameter. any other Mopar knobs of a similar era what would fit will be cracked just like mine are due to Arizona sun and heat. I guess I need knobs from some junkyard donor KJ from a region of the US that does not have the environment seen here in AZ.

Here is what the heater control panel looks like. All three knobs are identical and interchangeable.

I know this is not an MJ question, but I need guidance from one of our experienced members here. My wife’s 2004 KJ has cracked heater control knobs. The heat and the sunlight are the culprits, and any junkyards here in AZ all have knobs in the same condition. Anything on eBay only lists complete heater control assemblies, which is overkill for wanting three new knobs. does anyone know of a source for either new or used good condition knobs for this old KJ?