Have a bit of a knock or something on a new 4.0 in an 88 XJ. Piston slap? Worse?

It goes away above about 1500rpm and isn't there when the engine is cold. Once the engine warms up it comes on slowly. Sometimes it'll go away for a while if the engine is revved and then a few minutes later it'll creep back.

http://www.youtube.com/watch?v=http:...?v=HPkFOpUUdyQ

 

cracked exhaust manifold, if that slight hissing sound is part of what youre talking about.

 

Nope. New exhaust manifold. The hissing i think is just poor mic quality.

 

No one else wan't to take a crack at this?

 

47 views and no one even wants to guess?

 

well since you just want a guess, im thinking maybe you installed some new percussion pistons?

 

ahaha!

 

Still nothing huh? There has to be someone who's seen this before.

 

yup, figured i'd throw a little comedy in there

 

I didn't hear anything.

 

Sounds like a washer vibrating in a loose bolt somewhere.

 

Could be anything from ungreased pulley, bad engine mount, or throttle cable tapping the side of the cab. If it is a new engine it could possibly be a lifter that has losened or wasnt properly secured and the valve is slapping. That would be the first thing I'd check.

 

If its a auto(aw4) torque converter bolts are loose, first. If not loose or not a automatic, alternator, second. if not alt. water pump or idler pulley. Take the belt off and start it. if its quiet its a accessory. The last area would be exhaust rattling on the cross member or floor? sounds like a alt. to me. Sorry for the ramble- a little drunk.

 

It's not piston slap. An inline six will not have much of a problem with piston slap.

 

To me it sounded more like a rubbing noise. I would call it something worse after the easy stuff is ruled out. Whats up with all the sarcasm in the Cherokee forum?