this was my first post when i got my 2000 and came here to get advice on lots of stuff.
i fixed most and its in nice shape, runs great. but it knocks when cold for a while. today i ran it hot and drained/filled the tranny again. while i was checking fluid i noticed how quiet it was running.it almost seems like its outside the engine but hard to tell.
an original comment was piston slap that i was not familiar with.

any other ideas?

 

Probaly piston slap. Never heard a 4.0L that didnt have it. Once the engine warms up it shouldnt knock as loudly, if at all. My 97 does the same thing. Knocks a bit when cold, but once it warms up its barely noticeable.

A cracked exhaust manifold, cracked flywheel and even a bad distributor can sound similar.

 

ive had exhaust leaks that ticked like a lifter click in other cars. this is more metalic knocking.
why would a slap get quiet?.i dont know how it happens, gets worse?, breaks?
i have a 98 with 130000, quiet no noise, my backup!! but it got a distributator+ so its a job if i need it huh?

 

Because aluminum pistons expand with heat....

 

Tis the season. Cold weather starts= piston slap!

 

Where does it seem like it's coming from?

One way you can find an elusive noise is to get a length of hose, stick one end up to your ear and move the other end around until you hear it. This is especially useful if the noise is coming from moving parts outside the engine where you wouldn't want to stick a stethoscope (like around the pulleys).

If the noise is inside the engine, you can further fine tune its location by getting a stethoscope from Harbor Freight for $4.

 

thanks again, you guys are taking the fear out of slap. tried the hose with nothing for sure. if it is outside it will show up in time i guess.
so my last real concern is the "331" and it will either happen or not so ill just enjoy the drive till?? !!
had fun packing snow on my driveway in 4 hi, working good. i drive till its hot and snow is flat!