Piston slap questions

2000 XJ, 4.0L, 120,000 miles Everything stock...

I'm a little rusty at diagnosing piston slap. Not to date myself, but the only engine where I have heard it was the 292 cuin 6 in my 1955 Chevy Sedan Delivery... Gee I wish I still had that truck.

I have been chasing this noise for a couple of months that I thought was a sticky lifter. I fed it Lucas oil additive, Marvel Mystery Oil and some other stuff too. The sound has gradually gotten worse, not better. Then after reading several posts here, I thought it could be a cracked flex plate or loose TC bolt. I verified the TC bolts and bellhousing to engine bolts are all tight, and there are no cracks in the flex plate.

Symptoms:
I get a rather loud knocking noise when the engine is cold and under load. It is hardly noticible if the engine is idling cold without any load. I went over the engine this morning with a stethascope while a friend held the throttle at 1200 RPM in drive, with his feet on the brakes. This is what I observed:

• Timing chain and water pump were quiet
• Noise was most evident about 2" to 3" below the head gasket on the passenger side
• The only noise on the driver side of the head was the valve and injector clatter. I can't get the probe into the drivers side below the manifold.
• After about 3 minutes of running (30*F ambient), the thermostat housing was 140*F (with IR gun) the noise was barely noticable under load.
• In 5 minutes the noise was completly undectable

Is this a typical set of symptoms for piston slap?

Would a piston slap be louder on the drivers side, since that is the side where the piston is traveling down after ignition?

Is 2000 one of the years that Chrysler had trouble matching their engine bores to piston size?

TIA,
MoFo

Sounds off. Piston slap is usually constant. Has it been worstening with the colder weather? What oil and filter are you running ? My jeep makes a slap type noise till it warms up and its related to oil flow. I use a thinner oil if I know ill be in the colder areas for a while. Also mine did a very similar noise with a blown exhaust gasket that would go away when the engine warmed up too.

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I'm running 5w30 with a wix filter. I have about 1000 miles on them.

bump

As the piston skirt warms up, it expands. Sounds like typical piston slap to me, that klok-klok noise?.

You live in a cold climate, winter's here, and it's gonna take longer for that skirt to warm up.

piston slap goes away when the motor is revved up regardless of a hot or cold engine. ie if you were to hold the the throttle slightly open after start up and not hear a knocking noise, but hear that same noise at idle that would be one way to confirm piston slap.