Jeep noise or something worse?

Hi all, after poring over old threads I decided to just describe my issue in full so someone might help me diagnose.

What I had previously assumed was something related to lifter or valve noise a guy at a shop described as a knock. I wanted to give you a quick description so maybe I can shine some light on it. I'm possibly selling this shortly, and wanted full disclosure now that this has been brought up.

2000 XJ, 4.0, Automatic, 227k

History: Cracked head from overheat prior to owning, replaced with Clearwater head, new lifters. Oil pressure is good and consistent. No starting issues, no power issues, everything seems to be great.

Sound: Loud, but not overwhelming tapping at low RPM under load while cold. In cold weather much more prominent (obviously?). In rhythm with engine RPM. Once the Jeep is fully up to temp it's nearly gone though possibly just subtle enough to blend in with normal engine noise. This has been the case for approx 2 years since the head was replaced. I don't drive it often at all, at most a few thousand miles in the past year or so.

Thoughts?

Sometimes lifters do not retain their 'prime', due to defect, or sludge, etc.

Did you do the head replacement work yourself?

Have you used a mechanic's stethoscope, or a stick method to isolate/pin-point if the tap sound is low, or high up on the engine?

Alaskan89XJ said:

Sometimes lifters do not retain their 'prime', due to defect, or sludge, etc.

Did you do the head replacement work yourself?

Have you used a mechanic's stethoscope, or a stick method to isolate/pin-point if the tap sound is low, or high up on the engine?

Click to expand...

I did the head replacement myself, yes. I replaced the lifters. Some said to not replace because the old ones would be "worn in" correctly, while others said might as well replace. I have not used any means to see quite where it's coming from, but I'll see if I can get a general sense today.

Also should point out, no oil issues, leaks, burning, etc.

Were your old lifter faces noticeably convex, or flat? Shinny, or dull on contact face appearance? Obvious wear pattern differences from one to another?

You might try Marvel Mystery Oil, or some such for a couple of hundred miles, and then some STP, or some such. Solved my old 258 cu. in. Model 17 lifter clatter that developed after a sludge issue only, (by the PO).

In the older Jeep engines, some would drop a quart of oil, and replace with a quart of ATF, and run at idle for only 10 minutes, shutting down, and replacing completely with new oil, and filter. Doing so with ATF will cause a big cloud of smoke, possibly causing neighbors to become alarmed, and call the fire department. Also, I would think with our more modern Jeep engines, lol, the various down stream sensors might get a coating, as well as clogging up the CAT, etc.

Alaskan89XJ said:

Were your old lifter faces noticeably convex, or flat? Shinny, or dull on contact face appearance? Obvious wear pattern differences from one to another?

You might try Marvel Mystery Oil, or some such for a couple of hundred miles, and then some STP, or some such. Solved my old 258 cu. in. Model 17 lifter clatter that developed after a sludge issue only, (by the PO).

In the older Jeep engines, some would drop a quart of oil, and replace with a quart of ATF, and run at idle for only 10 minutes, shutting down, and replacing completely with new oil, and filter. Doing so with ATF will cause a big cloud of smoke, possibly causing neighbors to become alarmed, and call the fire department. Also, I would think with our more modern Jeep engines, lol, the various down stream sensors might get a coating, as well as clogging up the CAT, etc.

Click to expand...

Old lifters seemed flat, didn't seem too worn from lifter to lifter. I would say dull on the face, but that's just my best memory?

I know location of the sound is probably important here, I'm going to see if I can't get a better listen after I get out of work

Looking through even more diagnosing threads and various googling, without knowing the exact location, this sounds like worn bearings somewhere right? All the usual suspects, including an 0331 replacement.

I have a video clip if anyone is interested in playing that game

Piston slap. It is a 4.0 thing.

That would be sweet, but I'm not as optimistic. This doesn't sound as subtle as piston slap, and it's not at idle. although there's almost definitely that too. Thing has 230k for godsakes.

I got a sweet deal on my '99 XJ. My boss was driving to Tellico, when a prominent tap became noticeable. He pulled over to a shop and they checked the valve train and could not find a thing. He ended up driving 1500 miles there and back, then parked it. He decided to go buy a brand new JK. I picked the XJ for $1700 with 4.10s detroit in rear, JCR front which bumper , roof rack and flex lite radiator with elec fan set up. short story long... Piston skirt on cyl 6 broke off allowing piston to rock in cylinder. Threw a junkyard motor in for $500 delivered. Runs like a champ now!

You're not making me optimistic about selling this thing, haha

This is quickly turning into a "tell me my jeep is knocking" so i can move on with my life type of thread.

I was planning on selling it because I never drive it, but now I'm second guessing that. I won't get crap for it.

OK, if not piston slap then...

My '91 that I had a few years back, 225K miles and had a light knock when I acquired it. Mostly at idle, and went away as RPM picked up. It got a little louder as time went on. I put 15K miles on it, then the guy I sold it to put another 10K+ before it spit the rod out the side.

I'm sure the future of this motor is looking similar to what yours experienced. The only difference is it's the opposite as far as the sounds goes; silent at idle, worse as the RPM picks up. Fades into the background past like 2.5k

Looking at 4.0 replacements now...I'm going to re-use the clearwater head so that's not a sunk cost.