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!!!!! 4.0 Piston Slap or Rod Knock?? Video Attached

7K views 18 replies 9 participants last post by  jeep_dude 
#1 ·
Bought this 2001 in December 2011 for my son. Four months later I got this knock I'm trying to identify and I'm preparing to pull the pan. I'll post picks and update the thread after I pull the pan.

10W-30 Valvoline and Mopar filters religiously.

So, anyone care to hazard a guess as to what the problem is before I drop the oil pan?

Thanks,
Ken

 
#2 ·
Jesus. Sounds kinda like a diesel. Does the sound get quieter with the engine fully warmed up? When I first heard it, it sounded like piston slap to me. In that case, you wouldn't really find any chunks in the pan. You would have to get the bore of the cylinder's measured.

Because you said that you have changed oil in the correct intervals, and that the sound sort of dies off when you rev the engine, my vote is for piston slap.
 
#3 ·
Broken piston skirt. With it running that long with a broken skirt is just trashing the cylinder too.
 
#5 ·
Have not drove it since the knock started. Been sitting in the garage.

Pulling the pan tonight. I'll update the thread with what I find.

-Ken
 
#7 ·
Hope you stroke it, and turn it into a 4.7

Op, you have a 2001 WK?
 
#9 ·
Well, here's the proof. Broken piston skirt. #4 piston forward side. Cylinder wall looks great from what i can see. Cross hatching is visible.



This sucks.

Looks like a donor motor is my future. Maybe a hone and 6 new pistons, rings and rod bearings?

You guys have any ideas?

Ken
 
#14 ·
Mine sounded the same way and also found piston skirt chucks in the oil pan. Replaced the engine with an ATK crate engine and I have to say its been a great enegine so far. Runs great and has a bit more power than stock, MPG stayed the same as well. ATK also gave me a 3 year unlimited milage guarantee.
 
#16 ·
Matt speaks the truth. Just got mine back, Matt - thanks for all the tips. She runs like a charm now, definitely worth the investment. ATK had it in stock and delivered the very next day.

As for MPG, mine actually improved 2 -3 mpg. Makes me think I had something else going on in there. But noticeable power improvement. Peace of mind knowing I'm covered for the next 3 years.
 
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