I'm new around here, bought the jeep somehow convinced it was just exhaust leak noise
spent some time researching the various knocks and ticks of the 4.0s, popped off the valve cover and all was operating fine there, compression checked out on all cylinders. It does it all the time, it only seems to fade under acceleration from a cruising state, and letting off the gas completely

I uploaded a couple videos for y'all to have a listen to. I think one way or another a engine swap/rebuild will be in order soon. Is there any engine related problems for the 1997 year, and what used 4.0 would be ideal to seek out for swapping?

http://youtu.be/9Tdli8A7IdE

http://youtu.be/YiAGhU9sWZU

 

Sounds like my 00 xj except quite louder...same exact noise though and ive been wondering what it is for quite awhile

 

How is the oil pressure? I would check the torque converter bolts and flexplate first for tightness and cracks.

 

https://www.cherokeeforum.com/f51/ho...ocking-125547/

Start with this.

 

Good call.

Also, try adding a qt of MMO next time you replace your oil.

 

My XJ is a 5spd, Unless an actual flywheel can be the issue too.
I've changed the oil, with MMO in it. The oil pressure is around 42psi while driving, 20 or so at idle

 

Flywheels are usually a lot thicker and lest prone to cracking, but I suppose that the bolts could still be loose at the flywheel to crank bolts- requires removing the trans or engine.

Also, before you remove the engine you could pull the oil pan and check each one of the rod bearings. With a noise that loud it will be easy to tell if one is loose.

If it were me I wouldn't be reving it that much- if it's really a rod thats bad you see it come through the side of the block soon.

 

I just had that sound, for me it was the 5th cylinder piston skirt. Had great compression on that cylinder but when i pulled the pan the skirt was at the bottom. I got lucky and was able to remove and replace it so I could get it back on the road (building a new motor for it now)..

 

The 4.0 is a very manly engine, it does not have piston skirts, it has piston kilts. And just like a regular kilt, if you look under it you will find a rod hanging there.

 

hahahahahahahahahhaahaahahahahahahahahahahahahahah ahaahah this is now in my signature

 

If it is a piston skirt, is it safe to drive on? It's probably to gouged to simply replace the cylinder now. Explains the magnetic slivers in the oil dipstick.

 

It is NOT classic pinging or pre-ignition. Some kind of repeating mechanical noise.

Reminds my of when I was a kid and I put cards to hit my bicycle spokes. Does Jeep use a rubber timing belt? Perhaps coming apart?

 

Hmmm...doesn't sound like an exhaust leak or loose flexplate to torque converter bolts (anyway, if you have a 5 spd, there is no torque converter), those noises are loudest down below...sounds more like a top end noise. If your engine is making metal, there is internal damage. Remove the oil filter and open it up and see what's inside (there is a special tool that will slit open the filter). Good chance there is an engine teardown in your future.