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2001 Jeep Cherokee 4.0L Limited Engine Knock Video

S

srpope80

NAXJA Forum User
Location
Tampa
Hello,

I am having a knock that is more apparent when the engine is cold, but I'm unsure of what the real cause is. I've heard rod knock, rocker arms, piston slap, wrist pins, etc, but I'm not sure what it could be.

Here is a video I took this morning when it was cold.

Details are as follows: 2001 Jeep Cherokee 4.0L Limited, 119,350 miles


http://www.youtube.com/watch?v=vDOyZwH1Fjc
 
Sounds like it's in the top end. I would pop off your valve cover and check all the rockers first thing and go from there. Is that something you're comfortable with doing?
 
Do you have any performance problems/symtoms related to your "knock"?

Looks like it's time to broom stick your motor.

If you are going to broom stick around the timing chain cover, be extremely careful....I'd like to hear back from you what you found.

I've got a noisy timing chain - only when the engine is cold and at idle - but it doesn't sound as bad as your motor. My loose timing chain causes a bit of a rough idle while warming up due to the valve timing being affected. When warm and at off-idle RPM it runs quiet and smooth as silk. ('99 XJ 4.0)
 
I have checked the torque on the rockers, and they appear to be OK. (I had previously replaced a valve spring) The pushrods have also been examined and appear to be fine as well.

There is absolutely no problems in the performance realm. It runs and drives PERFECT.... Love driving it, just trying to figure out what this knock is and take care of it to make sure it's reliable.

Someone else suggested I should pull the oil pan and check clearances? Thoughts?
 
My 4.0L '98 XJ is making the same noise. It goes away when warm. Yes, my header is cracked. It does not sound like a lifter tap, my brother has one of them in his 4.0L '01 Grand. I thought mine was more of a piston slap, or wrist pin. My friend that owns a garage, where I take it for inspection says it sounds like that to him also. It does rattle when it idles, but it has always done that. I am just going to run it till I have Catastrophic failure:explosion. Then I am just going to drop in a Rebuild from some place like ATK, or Jasper.
 
I hate to say this but if it's not in the top end then you know where it's likely to be. Mine made a similar noise before the #5 piston left me. The good news is that if you catch it now you can take care of it with just a new piston/rod. Or use it as a good excuse to make a stroker.

Pull the head and/or the oil pan and check your pistons and rods. It sounds like a double knock.

The risk you take with waiting for a catastrophic failure is putting a rod through a cylinder wall and no longer having a usable block to rebuild with, if that's something you're even interested in.
 
metaldemon7, was your friend able to do any further diagnosis to determine the issue? Does he think dropping the oilpan would be a good idea?

Milford Cubicle II, did the piston on the #5 cyl have a broken skirt? Does a double knock usually indicate a wrist pin or something?
 
Where is the mic located on your camera? When you put it beside your steering pump looking down the noise got louder, suggesting cracked manifold.

when the manifold gets warm and expands the crack provides a nice place for the metal to expand, and it seals up
 
Sounds to metallic to be a header crap, but anything is possible. Especially the rattle after he lets off the gas. manifold. I would start with the flex plate bolts. Then pull the valve cover and while its running try to narrow the sound down. You can push on a rocker over the push rod to see if the sound changes.
 
Check your damper pully, it may be hitting your timing cover. I had the exact same sound and upon closer inspection I noticed the damper pulley had moved towards the timing cover and scraping it.
 
No we did not check it out any further. It is most defiantly is a piston, or wrist pin. I'm to busy to rebuild it. I did enough of that when I was younger. I have three weeks off at the end of the year, so I think I am just going to let Tom replace it with a rebuild then. The rest of it is in really good shape. I had OK 4WD put a lift on it, and go over it about six months ago. They did mention the rattle, but said that some of them do that for years. Mine has rattled while idling since I bought it in '03. Good luck with yours.
 
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