97 Cherokee Knock (Unidentified w Video) help!
 

Hi all, I've been searching the internet for almost 2 weeks now to no avail. I have heard this sound on a few other videos floating around youtube but all just lead to dead ends with no fixes.

Little background.
1997 Jeep Cherokee Sport
119K
Auto, 4.0 V6
Oil Change about 500 miles ago with Non-Syn 10w-30

I bought this Jeep with about 107K and never noticed the knock/clang. It started to become pronounced around 112k and progressively became more audible.

The knocking can be heard from the oil pan, closest to the bell housing on cold start up until the engine has warmed up to full operating temperature. Usually by the time I get to work (50 miles) the knocking is barely audible, so it does change as I'm assuming heat changes clearances. The noise also increases with increases in RPM up until about 1,700 rpm when you can't hear it over engine/exhaust. I'm not sure if it's still there or if it's just being drowned out.

Last weekend I decided to do my rear main seal. No metal or debris in the pan, all main bearing caps were tight to spec, rod caps were tight to spec as well. I did notice some wear on the rear main cap and the next cap in line but no gouging or overly noticeable wear. There was some play side to side on all piston arms, no up or down play. While I had the flex plate cover off I checked the bolts which were all tight minus one. Tightened that one up and was hoping that was the culprit but no deal. The bottom end of the engine looked very clean for almost 120k, no sludge or buildup.

I did notice some play in the timing chain, mostly up into the sprockets but not down towards the floor. I'm not familiar with how much play the chain should have so that's up in the air. I sort of wrote that off since the noise is mostly heard in the back of the engine.

I'm grasping for straws with this truck now. Any ideas? Oil pressure is very good, 43 on the highway and around 30 at idle (full operating temp). No loss in power, pretty much runs like a top minus the knocking.

(Link Fixed) Youtube link.
Sorry it's not the best quality but it should give a representation of what's driving me nuts. Thanks all!

Video has no sound for me. I tried watching on here and right from youtube but still no sound.

Miles

Damn, sorry about that. My droid has seen better days. Let's try this again.

sounds normal to me

lol This is my first Jeep so maybe it is. The underneath pan area sounds like a diesel clinckity clankity.

I heard it, I have a 97 w/ 116k and it does it at first then goes away after being ran for 5-10 min or so , then it sounds nice after it goes away

Think I have the same knock developing in the newest Xj...haven't dropped the pan yet but will this weekend.keep us updated with the issue & if you find the culprit

My '99 XJ is doing the exact same thing at 271k. Gonna keep my eyes on this thread.

I'm glad you guys are noticing the sound I'm trying to explain and you're dead on. The clanking sound dissipates with about 10-15 min of driving, not 100% gone but not enough to know something was wrong. I may dive back into the pan again to see if I somehow missed something.

Additional things I've noticed:

Harmonic balancer does have bit of a wobble.
Headgasket is leaking oil outside the block on the passenger side.
Using a piece of hose against my ear to try to track down the clanking, it's most audible between the rear of the pan and the flex plate.
Runs 100%
I can hear the noise increase with rpm while driving up until the tranny shifts to second.
I tried a heavier oil (15w40) to see if it would quiet it down a bit with no change.

I mean maybe this is normal driveline noise for a 4.0 but something really sounds sloppy to me...

Keep me updated if you jump into the pan. I was just about to order a lift/tires but I held off on pulling the trigger in case I find myself needing a new long block.

How long has it been doing this? I'm on about 7k miles now...

What brand of oil filter do you have on it? If you have a Fram filter or any other crappy filter that can give you a rattling noise on start up. Because of a dry start. If you have a fram filter you should replace it with a Mopar, Wix or an Napa gold brand filter. Also when you checked the flex plate for loose bolts did you check the flex plate for cracks?

I'm running a a Mobil 1 extended life filter. Usually always run the Mobil 1. I tried the check for any irregularities in the flex plate but as you probably know its really difficult to to inspect laying on your back. I could be totaly wrong but it definitely sounds internal.

sounds like piston slap to me.

Yeah you should be fine with that filter. I know that checking the flex plate while it's still on the vehicle is a pain in the A$$. But I would get a really strong flash light and give it another look. It is very possible that it is internal. But with a little luck you won't have to rip into it any time soon. Keep us updated on any other symptoms or if you find your problem. Hope it's nothing major.
Good luck.