Welp, I officially hate vehicles.

2000 Cherokee (w/ the 0331 head.. which i'm finding out is PURE SHIT!#%@%).

Oil pressure falls off to 0 psi at idle... had the dealership do a leakdown test and compression test. Numbers were good across the board.

Just spent 350 bucsk to have the oil pump replaced (because the dealership siad it was was failing) and that did nothing... its still fallin off after the engines hit running temps.. so that means main bearings/seals?

blah... anyone got a 4.0 L head (0630) laying around?

 

Damn, sorry to hear bout all the trouble this jeeps been giving you lately. Check the sending unit maybe, or could even be a clogged filter. Just a couple simple things that I doubt would be it but never hurts to check. Hows the tcase problem? Good luck

 

4.0 blocks have had history of cracking internally causing oil to bypass.

just so you know....

 

the heads crack all the time under heat probs i have never seen a cracked block.

 

The heads 0331 (00-01) are notorious for cracking between cyls 3 and 4.

Ive checked the sending unit, replaced the oil, filter(s), oil pump/screen/tube.... i removed the valve cover. no cracks (visible). the problem all started after i ran synthetic in it once to "clean it out" for 500 miles.... shrug there is a guy with the EXACT same problem i'm having with his 2001 jeep and he's pulling his motor friday to find out the problem. hopefull his findings point me in the correct direction.

 

20w50 all year long.

good luck man. i can't imagine going through this kind of shit this recently after buying a vehicle.

 

4.0 blocks have a history of cracking?? Thats news to me. Do you know that from experience or did someone just tell you?

I've been on the Jeep scene for a while and not once heard of a 4.0 block cracking. I know some guys who wheel the living piss out of their jeeps. The 4.0 is usually the only thing that doesn't break. Pretty hard to break a huge chunk of cast iron. I'm somone has broken a block somwhere along the line but I wouldn't say the 4.0 block has a "history" of cracking.

 

 

the heads will crack pretty bad on some years, but i have had to replace two that the blocks had cracked in the oil galley within the last four years. i dont ask how it was done, cause i know the indestructability of those engines.

from what i recall, there isnt a pressurized oil port on the head (oil comes through the pushrods to the rockers) so i dont think that a cracked head will cause low oil pressure. coolant loss and low compresion, yes.

also want to check the cam bearings, if you ran synthetic to "clean it out" its a VERY Good possibility you broke loose alot of sludge, and it has stopped up an oil passage either in the block or near the cam bearings.

good luck on the diag

 

Now that you say that that is one of the firs things im going to tell the mechanic to check.

Thanks =]