So Ive been running my 89 xj 4x4 4.0 for about 7-8 months since I bought it and I've noticed that once the engine is warm I get a decently loud lifter tick or engine knock of some sort. I took a stethoscope to the block and head trying to figure out where the noise was coming from exactly without much luck. It sounded like it was coming all from the head.

I know head noise with the 4.0's is a given since it uses a flat tappet cam combo'd with lifters and pushrods but this seems excessive? It does not making any knocking or tapping noises when cold. Only when its fully warmed up. I sort of ruled out a cracked header already because the noise would be right away on start up and deminish when the engine warms up from what Ive seen in person. My 4.0 recently seemed to have gotten louder now that the warm weather is here. Im currently running 5w30 conventional and have yet to try 10w30.

My main question. Is it time for a head rebuild? If soo what do you guys reccomend?

In some cases it could be the flywheel bolt had backed out and is hitting the torque converter shield. That was my case, had a noise sounding like a lifter tap.

I did some digging threw videos on youtube trying to compare sounds and what I've come up with is it sounds dead nuts identicle to piston slap.

Another thing I have to add is that The knock is very faint when Im driving it regularly. Its only very noticable after I beat on it with some high rpms or high throttle blips and it comes back to idle. The noise cannot be heard at rpms exceeding 1200.

Jeeps make noise. You'll get used to it

I have the same noise...I hate it ...only can hear it at idle...not the engine I am sure. Going to pull the auto trans and see if it could be a cracked flex plate or bad balance torque converter.....Trust me... I will find the root cause... John J..

try some Marvel Mystery oil

This was mine. I did new cam, lifters and timing chain. Just roll with it.

Mine has always made the same noise. I have listened closely to other 4.0s and about every other one makes the same noise. It is a Jeep thing.

+1... it's a noisy engine. You learn to live with it.

Found it... cracked / broken flex plate...could not see it from the inspection plate... pulled back the auto trans...removed the plate. I am lucky it did not completely break loose, I am sure it would have sounded like the engine blew..

New Flex Plate, new bolts and new rear motor mount.... Anything else ??

Good thing you didn't ignore it!......

Yes me too..... This is a known problem....so this is the first place to look...
Thanks

You are 100% correct. FIRST place to look.

Here's how to do it.

https://www.cherokeeforum.com/f51/ch...xplate-172081/