AZJeff

My MJ has a HO engine from a 2000XJ in it. About 5K miles ago, I discovered I had a crack in the famous "0331" cylinder head from this vintage of engine that was causing coolant to get into the oil. I discovered this when changing the oil, and I noticed it was not the pure black that old oil exhibits. It was more gray, and its viscosity was "funny". At the time of this discovery, the engine was making no weird noises, nor showing oil pressure or temperature issues. I was fortunate in that I found it before it destroyed the entire engine, so I did the following: --New cylinder head from Clearwater Cylinder Head in FLA. Also included new valves and springs. --New lifters, rocker arms, and pushrods (old ones looked fine, but I was going full bore) --New crankshaft bearings for both rods and mains (Clearances with old bearings were within spec., but I wasn't taking any chances.) --New timing chain and sprockets (I was in far enough that this was cheap) --New high flow Melling oil pump With all of this done, the engine runs well, and generates acceptable oil pressures per factory specifications. In addition, compression numbers are pretty close to fantastic, running (literally) between 135-140 on all six cylinders) HOWEVER....I have a noise that has been around pretty much ever since all this work was done. It has not gotten worse during this time, and professional laboratory oil analysis does not show any unusual metallic levels indicating high wear. I cannot seem to capture a good clean audio of the sound, so this is a good video of a very similar sound to mine (but mine is not a loud as this.) Piston Slap Sound Here are the symptoms: 1. The sound is non-existent upon startup, and reaches its most noticeable level when the engine has been operating for anywhere between 5 and 20 minutes. After that time span, the noise diminishes to almost imperceptible. 2. It is worse in cold weather. In ambient temperatures below 60 degrees, the amount of noise is a bit more, as is the duration of the “noisy time period”. 3. It also will make the noise on a restart of a warm engine if it has sat for more than 5-10 minutes, but the noise will disappear within 5 minutes after warming up on the restart. I have checked the flywheel for cracks and/or loose bolts, with no issues seen. This leads me to believe it's piston slap, in spite of the fact that when i pulled the head, the cylinders looked just fine. So here are my choices to fix the issue: ignore it, as the engine can last 10’s of thousands of miles with the sound, assuming it is piston slap. This is what Hagerty suggests, based on my internet searches. pull the engine and do a total rebuild of the short block. I have an almost brand new head on it, so I don't need that part redone, but the machine shop work would be some serious coin. do a cylinder rebuild in the chassis. Pull existing pistons, hone cylinders, install new pistons and rings. This, of course assumes that the cylinders don't look terrible when I pull the head, but I think they are OK, because when I installed the new head 4k miles ago, they looked good. This approach is cheaper the #2 above, but has it's own risks, of course. So for this guys who are deep into engine sounds, causes, and cures, what say you?

What does the fluid look like? Is it dark brown, or does it have some reddish coloration still? If it's dark brown, and fluid change (or two) might help the situation. The first change should probably entail taking down the pan, and looking to see what kind of crud is on the bottom of the pan and the magnets on the inside surface. Trans fluid is supposed to be highly detergent, and should keep non-metallic crud in suspension for the most part. A healthy transmission should only have a very light film of stuff on the bottom surface of the pan. This is mostly composed of clutch material that settles out. If the pan is coated to the point that you cannot see the silver surface of the pan bottom, that's concerning. Metallic stuff (of which there should be VERY little on a healthy transmission) should stick to the magnets in the pan. It normal to have a fine coating of "paste" covering the magnets, but no chunks and no bright slivers. Since the pan only drains about 3.5 quarts at a time, you might have to drain, refill and run it and then repeat the processs several times to get as much new clean fluid as you can into the machine.

With that crack in the head, there is NO WAY that gasket is going to last for any length of time. This will happen for two reasons: 1. the portions of the head adjacent to the crack are going to move independently of each other. That will cause gasket damage. 2. once the coolant is hot, and under pressure, it will start exerting a new additional force of the gasket in a direction other than normal, and that will accelerate gasket failure. That head is junk and needs to be replaced. Unless, of course, you want to get REALLY good at changing head gaskets on a regular basis.

I 100% endorse Cruiser's thought on ditching the fragile heater control valve. Those junky things do NOT age well, especially here in AZ, where temperatures really make plastic very brittle. There are those Jeepers who will prattle on about how removing that valve will allow the coolant to circulate through the heater core all the time and thus decrease air conditioning performance. While that might be theoretically possible, I cannot say that I have seen ANY NOTICEABLE difference. (And I say this as a guy who uses his AC most of the time, since I live in Phoenix.

Engines if the 2.5 and 4.0 era are virtually NEVER “interference engines”.

I remember my dad's 1968 Ford Galaxy had a PS cooler adjacent to the PS pump. It was a simple loop of tubing with fins attached to it. From that, I can infer that you probably don't need a really gigantic radiator to cool the PS fluid. If that assumption is correct, a small aftermarket transmission cooler would be more than effective as a PS fluid cooler. I would mount it on the return side of the system, where pressures are lower, since a transmission cooler is not designed to handle the pressures the the "high side" of the PS pump can deliver.

Eagle, I am a retired mechanical engineer, and while I appreciate your situation, you gotta remember that the XJ/MJ engine compartment was not originally sized to fit the 4.0 Anytime I do virtually anything on the front of an XJ/MJ with a 4.0, I start by removing the mech. Fan shroud and the e-fan. It’s a case where the front of that engine is 10lbs of s##t in a five pound box.

Here is nice short video on how to do a compression test: Compression Test

Yeah, that was the place. It was a great source for stuff.

There used to be a junkyard here in the PHX area that specialized in Jeeps. I went to them when i was looking for a sway bar for my MJ, since some previous owner had removed the one it came with . I was surprised that almost ALL of the ZJ, MJ, and XJ chassis in the yard were already missing their swaybars. Apparently, they are a hot item, at least out here in AZ.

I was gonna ask this too. The crankcase ventilation system can handle blow-by to a certain level, and then after that, it's too much, and the usual symptoms show up, like oil out the dipstick tube, leaky distributor, oil soaked air filter, etc. Tell us how healthy your rings are with a compression test.

If you can acquire a brand new ZJ bar, that would be the best choice. Since you have connections at a dealer on the west side, are you saying that a brand new OEM ZJ bar is still available? Just curious.

I would be quite surprised if a sway bar was able to be "narrowed" (as measured end to end) or "widened" due to poor recovery practices without the vehicle showing signs of damage where the sway bar is attached to the chassis. After all, this bar is made from forged spring steel. One thing I noticed is that the brackets that are welded to the axle housing, upon which the lower end of the sway bar link is attached, seem to be made from a forging, and not from a stamping. (My MJ has a late model XJ front axle, and those brackets are made from heavy gauge stampings instead of what OP's axle has.) I am wondering if those thicker brackets are part of the cause here. Is there some sort of difference in sway bar attachment points on the axle that happened over the years, or between 2wd and 4wd front axles?

Send a couple of pics so we can study the situation better and offer suggestions.

I have done conversions from R12 to R134a on several vehicles, and I have done write-ups on this forum before, so you can search for those. I a nutshell, converting to R134a will require the following: 1. new R134a compatible refrigerant oil (use the same amount as called for with the old R12 oil) 2. new o-rings on ALL connections that are compatible with new refrigerant oil 3. a new receiver/dryer (accumulator) 4 new shrader valves on the charging ports 5. evacuation of the system to remove all old R12 and confirm you are leak free 6. installation of a charge of R134a. The amount installed should be 80% of what the amount would have been for R12. If you have questions, fire away.

Lexan or other thermoplastics won't be very scratch resistant, and some of them might even have UV light sensitivity, depending on what the exact thermoplastic of choice is used. For something like the race truck posted above, it's no big deal, because it's life expectancy isn't measured in years. For a regular street vehicle, though, getting a thermoplastic in sheet form that has scratch resistance and UV tolerance is going to be tough (and expensive).

Deleting a sway bar on a lifted vehicle is a VERY bad idea. Yeah, sway bars inhibit articulation over off-road obstacles, but they also LIMIT SWAY of the body in turns, and that's VERY important as the vehicle speed and ride height increase. If you want more articulation for off road, but some quick disconnect sway bar links from JKS or other suppliers. DO NOT ditch the sway bar.

Grease, plus airborne desert dust = tan glop over every item so treated. Then I have to get under the KJ and wash the grease off before applying a new coat Rubber issues aside, you should see the bottom side of the wife's 2004 Liberty. It looks almost brand new, with no corroded bolts and all original chassis paint still fully intact. When I do have to work on it, it's like taking apart a car that is less than 6 months old from places like Minnesota.

I replaced the entire lower arms on the wife’s KJ with Moog from Rock Auto. However, my main motivation was dried/cracked arm bushings, and having a new BJ already in the new arm was a bonus. Rubber bushings live a hard life here in PHX, as road surface temps regularly get to over 140 degrees.

A "pin hole" to me is something of about 1/8" in diameter or less. Under that definition, I would drill them out to be round (assuming they are not) and them put a "pop" rivet into the hole. Then coat both sides of the rivet with automotive body seam sealer. If there a bunch of pinholes all located near each other, i would not recommend this approach, and I would install a proper patch in the sheet metal instead.

Here are two things to consider: 1. The distributor gasket's purpose isn't to seal against pressure, it's to prevent weaping of oil from out of the hole. If you are seeing oil leakage immediately upon startup, and the leak is steady, the o-ring/gasket isn't designed to handle such leakage, and crankcase pressure might be the culprit. 2. The distributor clamp's job is to prevent distributor rotation once the timing is set correctly. The amount of pressure needed to keep the distributor stationary isn't very high, if all parts are in good condition. If you grab the distributor, and try to turn it by hand with substantial force, and it does not move, the clamp is doing it's job.

As long as the flange on the distributor housing is in firm contact with the machined surface on the engine block, the o-ring should seal no problem. The forked clamp really plays no part in determining leak resistance other than making sure the distributor stays seated on the engine surface. If you are still getting leaks from your distributor, I have to wonder if your crankcase is getting pressurized due to the crankcase ventilation system being plugged up. Have you ever checked to make sure that the crankcase vent tube between the valve cover and the manifold is not restricted? One sure sign of crankcase vent problems is that oil vapors leak out around the grommets in the valve cover, and/or the air filter box is full of oily residue.

Assuming one cannot find a corner from a rusty bed, any SERIOUS body shop could fabricate a replacment corner using an "English Wheel" It wouldn't be cheap, but a new corner could be created and then welded into the existing bed. This method is often used in older vehicles where replacement parts are nearly impossible to find. However....given the relative ease at finding a trashed rusty bed from an MJ that still has good corners, the approach I suggest would be a last resort, unless you have lots of extra cash laying around.

I have a RockHard bumper on my MJ. I don't have the brush guard/bull bar for it, but it's a bolt on item that can be added as needed.

A small piece of plastic sheet stock, or thin aluminum can be painted and installed with small screws or "pop" rivets to block the hole. I did that on my dash where a previous owner had installed a big bracket for a two way radio microphone. Once painted to match the interior, it's barely noticeable.