4.0 Piston Skirt

[timsjeep]

2000 Cherokee 4.0 200K miles

I just blew a piston skirt and need some advise. This is not a daily driver but I'd like to keep the truck as cheaply as possible. The rest of the motor seems to be ok, there was no noticeable metal dust in the bottom of the pan. Oil pressure is good. The cylinder wall of the broken piston looks ok (to my inexperienced eye), the area where the broken skirt was rubbing has lost some of it's mirror finish but it's unnoticeable to the touch. Am I going to waste time and $ on replacing the piston(s) or should I just buy a running junk yard motor?

Thanks guys!

[4.3LXJ]

It would depend on how much of the skirt is gone. But if you are getting wear that can be seen, I would guess that eventually it is going to start slapping

[Mudderoy]

I'm guessing it would be new piston, rings and cost to have the rod pressed on the new piston. Head removal, hone the cylinder. Head gasket and maybe new head bolts. Assuming the cylinder wall isn't badly scored and honing it would remove any damage. So what would that be $300, $350?

The only problem with a junk yard engine is you just don't know what you are getting. You may wind up replacing the motor a couple of times.

[LizardRunner]

I would replace that piston, you are now in an out of balance situation which will create more problems.

[xj4life2]

If it were me I would pull the pan and drop the offending piston out the bottom ,lightly hone the cyl and replace the new piston. This should take a few hours and save alot of $$'s. You will know quickly if this fixed the issue and a new motor is in your future. But it will allow you to run the rig a while. As Steve said it may start to slap after some time but I have done it this way on a couple of XJ's and they are still running today with no issues. Good Luck !!

[LizardRunner]

If it were me I would pull the pan and drop the offending piston out the bottom ,lightly hone the cyl and replace the new piston. This should take a few hours and save alot of $$'s. You will know quickly if this fixed the issue and a new motor is in your future. But it will allow you to run the rig a while. As Steve said it may start to slap after some time but I have done it this way on a couple of XJ's and they are still running today with no issues. Good Luck !!

Yep that is the easy way to fix it. I've had a few engines that I had to do this too and they lasted well afterwards.

[Mudderoy]

If it were me I would pull the pan and drop the offending piston out the bottom ,lightly hone the cyl and replace the new piston. This should take a few hours and save alot of $$'s. You will know quickly if this fixed the issue and a new motor is in your future. But it will allow you to run the rig a while. As Steve said it may start to slap after some time but I have done it this way on a couple of XJ's and they are still running today with no issues. Good Luck !!

That's nice to know. I didn't think you could get the piston out the bottom, but I've never had a 4.0 apart.

[timsjeep]

That's great news. I also did not know that the piston could be replaced from the bottom. I'm going to try it as I'm not having luck finding a replacement motor. The only one I've found in town (Phoenix) is $1200 with 115K. That seems like twice as much as it's worth to me. Thanks guys, I'll post my success or failure.

[Mudderoy]

That's great news. I also did not know that the piston could be replaced from the bottom. I'm going to try it as I'm not having luck finding a replacement motor. The only one I've found in town (Phoenix) is $1200 with 115K. That seems like twice as much as it's worth to me. Thanks guys, I'll post my success or failure.

:wow: $1200 I was thinking $500 to $650. I bet you could rebuild yours for $700 to $1000, and that would be ZERO miles.

[OrangeXJ]

If it were me I would pull the pan and drop the offending piston out the bottom ,lightly hone the cyl and replace the new piston. This should take a few hours and save alot of $$'s. You will know quickly if this fixed the issue and a new motor is in your future. But it will allow you to run the rig a while. As Steve said it may start to slap after some time but I have done it this way on a couple of XJ's and they are still running today with no issues. Good Luck !!

What he said /\/\/\. $1200 bucks for a JY engine is bull shit I got a re- maned 4.0 for $1095 with a 3 year warrenty.

[belvedere]

Unfortunately, I'm in this situation now myself. Broken skirt on #6 piston. Can the piston really be replaced from the bottom? Doesn't look like there's room, but I haven't actually tried.

[4.3LXJ]

You have to take the head and pan off. You undo the connecting rod and the piston comes out the top

[belvedere]

You have to take the head and pan off. You undo the connecting rod and the piston comes out the top

That's the way I've always done it, too. But according to a couple of the above posters...

[timsjeep]

Unfortunately, I'm in this situation now myself. Broken skirt on #6 piston. Can the piston really be replaced from the bottom? Doesn't look like there's room, but I haven't actually tried.

This worked for my jeep. I have about 500 miles on the motor after the fix and it it still purring. However, this is a lot of work on your back if you don't have a lift. I had particular problems removing and replacing the oil pan around the front axle. If you can find a lower mileage motor for $500 or $600 I think you may want to go that route because its going to be the same amount of work and not much more money.

[denverd1]

wouldn't the pan have to come off anyway to push it out the top? does sound like a lot of work and you still have 5 others with miles on 'em. I've seen 4.0 engines go for $400 locally and someone is parting out a grand cherokee w 4.0 right now.

[belvedere]

This worked for my jeep.

So you removed and replaced the piston from the bottom? I have the pan off, and yes, it took some effort to get it out!

[timsjeep]

Yes the pan has to come off, along with poping the exaust. Some guys get away without having to jack the motor up but in my stock 2000 cherokee, the motor had to get pushed up 4 or 5 inches between the motor mount and the frame. But then again- if you know the skirt is broken, you have already gotten this far:)

The piston for mine was like $60, the rings (had to buy the whole set for my year/motor) were almost $100, I paid a local shop $20 to heat and press the piston/connecting rod together, then add a valve cover gasket, head gasket, oil pan gasket, and you are knocking on the door of $400. Then you're not even sure if that will get humpty dumpty running again! If you have a motor for $400 locally, my 2 cents is to swap.