Knocking after cold start up

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Nov 21, 2014 | 03:18 PM

#31

Stabsthedrama

Seasoned Member

Joined: Aug 2014

Posts: 486

Likes: 1

From: Lehigh Valley PA

Year: 1989

Model: Cherokee

Engine: 4.0 renix

Again, try to pinpoint the noise. If you're not planning on rebuilding the engine anyway (I'm sure you aren't) then knowing what it is or at least what it could be is very helpful, and I'm sure a lot of guys here would know even more about it. Pinpointing it, when it happens, or possibly getting a video of it would be a good idea.

The bottom end "fwap fwap fwap fwap fwap" (that isn't too loud) for example, is pretty damn common especially on the older 4.0's, and many have the noise for 200k+

Lifter tick is another (usually) somewhat harmless noise that can be lived with if it only happens from time to time, and isn't usually worth rebuilding a head for.

Otherwise make sure to have good oil and a NAPA or Wix oil filter - no orange cans of death, etc.

Later on after some research you may decide to do some marvel mystery oil or something more aggressive like restore or possibly seafoam, and this might help free it up pretty good, but doing a bit more poking is needed first (and a wet/dry comp test)

Nov 21, 2014 | 03:42 PM

#32

phishy

Member

Joined: Oct 2014

Posts: 361

Likes: 0

From: Delray Beach, FL

Year: 1997

Model: Cherokee

I feel your pain and your anxiety. I bought an XJ recently at it's got a quiet knock coming from the bottom end once mine warms up. I've since written it off to it being a 4.0 and the fact that most of them make odd sounds. And on the flip side of things, if it is a rod knock it will get much louder before it lets go usually. Chrysler engines are good about this. My dads Dakota has been ticking and knocking the last 200K miles (he's got around 320K on it now).

Nov 21, 2014 | 03:49 PM

#33

salad

Herp Derp Jerp

Joined: Nov 2011

Posts: 18,251

Likes: 17

From: Parham, ON

Year: 1999

Model: Cherokee

Engine: 4.0L OBD-II

Quote:

Originally Posted by TFitzPat87

Unfortunately that's the problem! When I'm sitting at idle (park or drive) the sound is gone. It didn't go away after revving for a second, It stared out of nowhere and I could only hear it while on the gas, then it got quieter and was gone after 1 or 2 minutes (this is what happened Thursday). The first time it happened (Tuesday) it happened out of nowhere as well when I was pulling into a parking lot. I parked, did my thing, left the store, and the sound was gone. Both times I heard it I noticed the XJ was almost warmed up but not completely (maybe 180 or 190 degrees on the temp gauge).

Is it easily reproducable? This would be an excellent use for an audio recorder or camera: Go for a few drives with it in the engine bay, you'll at least narrow down the region.

Nov 21, 2014 | 04:01 PM

#34

TFitzPat87

Thread Starter

CF Veteran

Joined: Apr 2014

Posts: 1,419

Likes: 1

From: Detroit, MI

Year: 1997

Model: Cherokee

Engine: I6 4.0L

Quote:

Originally Posted by salad

Is it easily reproducable? This would be an excellent use for an audio recorder or camera: Go for a few drives with it in the engine bay, you'll at least narrow down the region.

Nope, I haven't been able to reproduce the sound. Just took me 50 minutes to get home and it didn't happen. That was pretty much the point I was trying to make to Stabs is that I can't reproduce the sound when I actually have the time to stick my head and ears in there. I'm not really able to just go out and see where it's coming from.

So far is very occasional and doesn't last long.