AZJeff

I am skeptical of the cam being trash, and here is why: I know that many guys feel the older flat tappet cams don't do well with modern oil, but I never had any issue with it on my two XJ's, both of which clocked over 100K on them. However, when I pulled the lifters to clean them when I put on the new head, they were RASTY. What I mean is they had varnish on them that was so bad, I had trouble removing a few with the lifter "slide hammer" gadget. After I got them out, they were just plain gunky on the top side, and I did my best to clean them with acetone, and then soak them in ATF before reinstalling them. The bottoms of the lifters where they ride on the cam were flat and smooth. It was obvious that they were still turning as desired, with no wear patterns showing. I almost think my "cleaning" of them may have actually made one or two of them MORE problematic, especially since I did not disassemble them in any way. In retrospect, I should have ignored the old adage about not putting new lifters on an old cam, and just replaced them all. This is me postulating (hoping?) that the issue of cruddy/semi-inoperative lifters is the source of my noise....

That is correct. When I start it cold, there is no tap. After a couple of minutes (no more than 5), the tapping begins. It "peaks" and remains constant until the engine is VERY warm (and you know what "warm" means in PHX.) Once the engine is really good and hot (temperature guage has been at 200-210* for more than 15-20 minutes, and idle oil pressure is now about 20 psi), then tapping sound is "almost" gone. If you listen CAREFULLY, you can hear it, but its no where NEAR as obvious as when in the "warm up" phase. Even my wife commented on the tapping in warm up phase, but she could no longer hear it on a hot engine (but I knew what to listen for, and detected it FAINTLY when hot).

I did not MEASURE them, but I inspected the ball ends for signs of wear, and saw none. When I stand them up on a hard surface, the heights are within 0.005" of each other, roughly. The pushrods I put in were new Melling ones, from Rock Auto.

I just finished taking out each pushrod, and blowing them with the air compressor. They are clear (which makes sense, since the pushrods were new when I installed the head 18 months ago.)

Clear? Meaning free of obstruction and/or not bent? Yes to both.

Well, I think I found the problem, or a least a major contributor: Intake pushrods on #4 and #6 aren't gettting hardly any oil up onto the rockers. I ran it for about 1 minute, and all the other rockers had plenty of oil accumulating in the low spots. Those other two were damned near dry (other than what had splashed around prior to the valve cover removal. I think a set of lifters are the order of the day, don't you?

Roger...standby

Cruiser, I just went out and ran each cylinder through TDC, and confirmed that the pushrods spin (and do not appear to be bent) when in that position on each cylinder. The pushrods were new when I put on the new head, so I don't "think" they could have gotten bent when I installed the new head and valve train. When I did the head, I thought "don't mess with the lifters, since they are run in on the cam" and the old adage was "don't swap lifters between lobes, or put new lifters on an old cam". (I realize this old adage is probably no longer applicable.) When i cleaned the lifters, I did so in acetone, and I will admit, they were somewhat varnish coated, and were tough to get out of their bores with the normal lifter removal tool. There was no scuffing or cupping on the bottoms of the lifters, and when peering down with a flashlight onto the lobes of the cam, I saw no signs of wiping on the cam (but of course, that wouldn't preclude lobe wear.) Whaddya think?

When #6 is at TDC (verfied by copper wire into spark plug hole), the rods will spin, but not move radially at all (which should be normal, correct?)

I acknowledge that I really don't know WHAT this engine is made from. I know it has the late intake, and had the late head (the 0331 that cracks when overheated), but the cam/crank/pistons may be a mish-mash of stuff, for all I know. I remeasured all the lifts again, and here is what I get:

As my sig says, I have a 2000XJ engine/control system in my MJ, so the specs. I quote are for that year of engine (I have the Mopar shop manual for the 2000XJ). However, you are correct in that my noise seems to be eminating from around #6.

So I tried to measure valve lift at the valve spring retainer, but I could not get a good consistent spot with the tip of my dial indicator. So...back to a more complex, but consistent approach: 1. remove rocker bridge and the two rocker arms for a given cylinder 2. install dial indicator tip into hole on end of pushrod, and measure pushrod lift 3. multiply measured value above by 1.6 (the factory rocker arm ratio) to arrive at actual valve lift Here is what I came up with, and it's not pretty. Not a single pushrod lifts to the specified height, which means all the valves are not opening to the desired amount. Even if the lifters themselves are clean and functioning normally, I think my camshaft may be toast. Comments?

I used Mobile ONe in two XJ's I owned for many thousands of miles (here in PHX, the temperature endurance of synthetic is a significant bonus). I never saw any cam issues. Then again, I never had an engine with coolant contamination of the oil. I will pull the valve cover, and I will measure the lift on each pushrod with a dial indicator, and compare against the shop manual spec. I will report back in a day or so.

I did as you suggested, and recorded a cold start. Here is the video (mostly for audio value). As you can hear, there is virtually no ticking sound. Then I shut it down, and waited about one minute, and did a restart. The ticking starts up relatively soon after the restart, as you can hear. Cold Restart.m4v Cold Restart.m4v Cold Start.m4v

Mobile One 10w30 and a Mopar filter.

I will let it cool and try that, and advise. Thanks.

I get the idea of looking at the flex plate with my camera. Once the engine cools, I will dive into that. (Even though it never changes the noise between loading the engine versus no load.) But on the lifter inspection, what are you suggesting I will see? A pushrod flopping around under the rocker, or something else? Wouldn't that be most likely detected by looking for lash to return very shortly after the engine is shut off?

So I have added two short videos of the engine running (really all that is needed is the audio). The first one is after the engine had been at operating temperature on the road for about 20 minutes. The second one is of the engine on a hot restart after it sat for about 5 minutes after I shut it off from the 20 minute road trip. Hot Restart.m4v Hot Running.m4v

It’s an AW-4. I know the diff between a flywheel and a flexplate, and used the correct term. Besides which, I don’t think 4.0 flywheels crack around their mounting holes in normal use, unlike the flex plates☹️

I considered piston slap, as I had an XJ with some of that, but it slapped pretty much all the time at idle speeds. But let's rewind the tape a bit, and give the history of this engine: After purchasing the vehicle a few years ago, and spending about 11 months making it roadworthy, I took it for a shakedown cruise to a car show where my son lives, about 300 miles away. All went well. I had put fresh oil (10w30 Pennzoil) just before the trip. When I returned, I decided to change the oil. What came out was.....odd, sort of like a very thin pancake batter. I sent a sample off to Blackstone oil labs, and they confirmed my suspicion--I had coolant contamination in the oil. Knowing this was an engine from a 2001XJ that had been transplanted into my MJ, I did the recommended "0331 head" inspection, and found the classic crack in one of the rocker bosses on #4 cylinder by using UV light. So...off to Clearwater Cylinder head for a new head and valve parts. I also purchased new rockers, rocker pivots, and pushrods. WHen I disassembled the engine to install the new head, I noticed some signs of what caused the crack---some evidence of a previous cylinder head gasket failure and streaking of coolant down the manifold side of the block. I also noted the head gasket that I removed was NOT a Chrysler gasket, but was Fel-Pro. Someone had obviously been into the engine to deal with some sort of overheating failure previously, but was not aware that such an injury to a 1999-2001 "0331" head would almost certainly crack the head. I inherited that issue. When I did the new head, I also took all the lifters out and cleaned them in lacquer thinner on general principle, dropped the pan and installed a new RMS, and a new Melling oil pump, and cleaned the pan and put in a new one piece pan gasket. While I was down there, I dropped a rod cap to check the #6 rod bearing while I was doing the rear main. Except for a bit of dirt embedded in the shell, the bearing look ok, and not wiped in any way. I did NOT check clearances on the rod or the main. I checked for the classic signs of piston slap by turning the engine and watching for cocking of the piston skirt, and did not see any. The cylinder walls were perfect, and there was little to no carbon on the pistons, and no ridge on the cylinder walls. Once the engine was reassembled, the compression on all six cylinders was between 140 and 143 after an initial run-in. I figured all was well. The noise started up shortly after the new head was installed. I run Mobil One 10w30 with Mopar or Wix oil filters. The engine is smooth, with no shaking, no oil consumption, and no coolant losses. I am kind of mystified, as I would think that a sloppy piston would cause the compression readings to be a bit more varying. Input is still welcome.

OK, I did your suggested test. I waited until the engine was fully warm (where the noise is normally virtually gone), and I shut it off. Then I restarted it after about 10 seconds. The noise was unchanged, and was almost inaudible. I repeated the test, but instead of waiting 10 seconds, I waited about 1 minute. Upon restart, the noise appeared for about 3 seconds, and then disappeared. Lifter leak down? I found a video on YouTube of a guy with a TJ that has almost exactly the same noise/location, but he has not yet figured out what it is. Here is the link to his video (mostly useful as audio): TJ 4.0 Noise

I wondered about the lifters. I put a new head on it about 2 yrs ago (famous “0331” head crack) and put new pushrods/rockers on it, but just cleaned all the existing lifters in lacquer thinner and then soaked them in oil before reinstalling. I have a camera with a fiber optic. I wonder if I could see the crack in the flexplate somehow with that device....

It’s a 2000XJ engine, with OBD-2. It has new exhaust manifolds and the trick gasket some guys on here recommended (I cannot remember the brand name). The engine has the Calif. emissions package for a 2000XJ, so it sports two cats, one hanging off each bank of three cylinders. I have checked for cracks where the two cats join up to the exhaust pipe.

My 4.0 is making a strange ticking noise near the back of the engine, and it has a strange pattern to it. Let me describe the sound: it is not as metallic as a lifter, and it’s too. Low down in the engine to be valve train. It’s not as deep or dull as a main bearing knock. Engine load (or lack thereof) does not change the noise, so it’s not a rod issue. None the less it’s a sort of tapping sound, but with a temperature component I will describe below. When I first start the engine, the noise is not present. As the engine warms up, the ticking is audible, but only at idle. Once the engine comes even slightly off idle, it’s inaudible, and of course as engine speed increases, the general engine and road noise may be masking it. When the engine is FULLY warmed up (running for 20 minutes or more on the road), the noise is no longer audible at ANY engine speed. If I shut the (fully warmed) engine off and restart it within about 5 minutes or less, the noise remains gone. On the other hand, if I wait longer than 10-15 minutes and restart, the noise reappears again until the engine re-warms, at which time it disappears. Oil pressure is good (within spec.) and compression is uniform at 140 +/- 3psi on all six cylinders. My stethoscope investigation points to the noise being near the back of the block, but I cannot pinpoint it. Any suggestions?

A 4.0 cooling system will do an "acceptable" job of keeping the engine at normal (design) operating temperature, even with air conditioning, and even in extreme temperatures. I live in Phoenix, and have had three XJ's and MJ's that have successfully operated in a climate where daytime temperatures regularly go over 110*, and pavement temperatures are regularly above 140*. The key to a successful cooling system is one where ALL the OEM components are operating as designed, and therein lies the trick: many owners neglect little things like a worn viscous clutch fan, or a missing mechancial fan shroud, or a slightly degraded radiator. I have found the the following combination of OEM parts to be quite effective 1. regular water pump (and major brand is just fine, and there is no need to spend money on something fancy) 2. a fully functional viscous clutch 3. a proper fan shround 4. the electric cooling fan that was found on later model XJ's 5. a new EIGHTEEN pound pressure cap (on an open system) 6. a quality 195* thermostat I do deviate in one way from OEM parts---I run a CSF all-metal 3 row radiator. I cannot say if it works any BETTER than an OEM, but at least the plastic tanks won't degrade in our intense heat here.