cfurnell

Forgive me if this has already been answered. I've spent the past 2 days trying to find info on the forum. Although I haven't dropped my oil pan yet, I am pretty sure I have a broken piston skirt. My question is, is it possible to JUST replace the broken piston? And if so, what is involved in that? I have a 02 WJ 4.0. Thanks for any info you can provide.

dave1123

Yes, you can just replace that one piston. You'll have to pull the head, pull the oil pan, take out that one rod bearing, and pull the piston from the top. Check the cylinder wall for damage and anything the pieces may have hit on the way down. An automotive machine shop will fit a new piston to that rod. You'll need new rings for the piston and a bearing if yours is damaged. If the bearing is damaged, inspect the crank for damage.

When reinstalling the piston, BE VERY CAREFUL NOT TO NICK the crank with the rod bolts!

If the piston skirt was the only failure, the head will probably still be okay. I don't think an 02 is ready for a total ring and bearing job yet.

jebmccall

yes its possible to do just one, thats how warranty has you build an engine when the head drops a valve seat. the other 5 may go another 50k or my go another 5 miles before the next one fails, or the others may never fail. in my opinion this is what i would do.

lets say engine has 100k while i was in their id change out all the rod and main bearings, check the cylinder bore for damage/signs of wear, clean carbon off all the other 5 pistons.

if it has 200k id do all bearings including cam, inspect cam lobes for wear, go on and change all the pistons new rings obviously. change the oil pump and call it good to go.

dave1123

You forgot timing chain and gears.