Oil Pressure

[Crate]

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?

[dubwize]

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

[HatefulMechanic]

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

just so you know....

[Ninety7GSX]

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

[Crate]

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.

[mudstuck98]

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

just so you know....

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.

[dubwize]

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.

:stupid:

[HatefulMechanic]

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 :thup:

[Crate]

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 :thup:

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

Thanks =]

[CHAHONDA]

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

Thanks =]
if needed i can get you a motor for cheap! with low miles too!

[Crate]

I will DEFEINTLY be asking you if I need one. =]

out of curiousity... what year and how much?

[CHAHONDA]

I will DEFEINTLY be asking you if I need one. =]

out of curiousity... what year and how much?
how about an 2001 model for $400 :D

[Ninety7GSX]

Can't beat that with a stick. :p

[Crate]

how about an 2001 model for $400 :D


I'll call you Tuesday when I find out whats wrong with my motor. If its anything more than just some cam seals or something like that i'll PM you. =]

[Crate]

Got a mechanical gauge on it today... drove it around for a bit... at FULL hot temp when the gauge on the dash read 0psi it was 5psi on the mechanical gauge. Put in 20w50 and some Lucas and now at hot it doesnt go below 14psi (which is actually in factory spec)... so i'm gonna toss a mechanical gauge in just to keep an eye on it while i'm on the beach and such and just run 20w50 until I start to notice anything funny, or until I get a huge urge to open the motor.

[HatefulMechanic]

a month and half later......



i have had three 4ohs in here over the last few months, all with the same symptoms. cam bearings every time.

in fact, i have an 01 sitting here now with the engine on a stand. cam bearings are about 45 bucks (clevite) and takes a few hours to install them with the engine out.

back on the lot it goes. figured that may help ya a little.

[Crate]

whats the cost on replacing one of those? I dont feel like fuckn with it. =]

[HatefulMechanic]

usually about 10 hrs labor, and about 40-50 bucks in parts.


around here, that equals about 500 bucks. but at most shops, esp. in real places, you are looking 700-900 buckeroos.