WHATS THIS NOISE? Timing chain or piston slap? - JeepForum.com
 
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post #1 of 5 Old 08-22-2008, 04:50 PM Thread Starter
4.0H.O.XJ
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1996 XJ Cherokee 
 
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WHATS THIS NOISE? Timing chain or piston slap?

At the front of the engine. In the timing chain area.

Used to do it ONLY when COLD, but now it is taking longer and longer for the noise to go away. Today, it didnt go away at all. Sounds like marbles in a can of light oil being rattled around. Been doing it since I bought it and has slowly gotten worse.

Yes, it sounds like a timing chain.

However, another Jeeper said: "No. a '96 timing chain is virtually indestructable. What you are hearing is PISTON SLAP."

Doesnt sound like any piston slap Ive ever heard, and with 217 thousand miles on it, I'd be inclined to think "timing chain." He says piston slap. WTF?

Advice and or input is appreciated before I find myself in a full engine teardown when all I needed was a timing chain. For what its worth, engine runs perfect, oil comes out clean and amber every 3K miles, 40-60 PSI oil pressure, runs at 200 degrees all day long. Good compression and no other engine noises. Runs PERFECT otherwise.

Thanks

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post #2 of 5 Old 08-22-2008, 05:24 PM
tjwalker
It's the crank sensor!
 
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Have you used a mechanics stethoscope on your engine yet to help isolate it? Engine noises can be tough to track down and if it is piston slap, a stethoscope should be able to isolate it to a certain cylinder.

I believe piston slap usually gets a bit better as the engine heats and metal expands. Doesn't mean that it isn't piston slap that has reached a certain wear point where it stays noisy I suppose.

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post #3 of 5 Old 08-22-2008, 06:03 PM
balloo93
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Check the harmonic balancer and make REAL sure it's not walking back into the timing chain cover.

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post #4 of 5 Old 08-22-2008, 08:48 PM
vinceleonard
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1987 XJ Cherokee 
 
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my cherokee was doing the same thing and the front two rod bearings were bad. i bought a set of stock bearings and a high volume oil pump since i was loseing pressure.now it runs 30 lbs of pressure after it's hot and doesnt rattle anymore.i did this in the cherokee in a couple of hours.the bearings were like four dollors a piece for each rod and the oil pump was close to seventy.i'm hopein it will hold me until i can come up with enough money to get a rebuild.hope this is of some help.
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post #5 of 5 Old 08-22-2008, 09:05 PM
Paul_C
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Since you're familiar with the knock sound of piston slap and I would agree that doesn't sound like marbles in a can. I might suspect one of the engine accessorys like the water pump, alternator, idler pulley, ect.
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