Just bought my first xj its a 2000 with 4.0 180000 on the clock
Problem is its got low oil pressure it was at 0 at warm idle and on the pressure tester it was at about 10 it goes up with rpm though the old owner re did the bottom end and cam bearings and put in a high volume oil pump. I am running 5 quarts of 20w 50 and a quArt of Lucas oil. Would puttin in the oe oil pump fix this problem? Now for the ticking one mechanic said rocker arms and another said timing chain guides. It's not a loud noise but it sounds like a diesel truck
Any help would be greatly appreciated
Also I heAr replacing my oil filter with a napa gold one or mopar one would help

 

You have a 2000, which from the factory came with the infamous 0331 cylinder head. That head can have a bad habit of cracking between cylinders 3 and 4, where there is a casting defect.

Are you using any coolant? The #1 symptom of a cracked 0331 head is "unexplained coolant loss". If the head was the root cause of the problem and it was not replaced, you may be spinning your wheels here.

When that head cracks, coolant mixes with the oil and can take out EVERY bearing in your engine and that results in low oil pressure.

The spec oil pressure for the Jeep 4.0 is no less than 13 psi at HOT idle and between 37-75 psi over 1600 rpms.

 

I have an '04 with the similar oil pressure of 4 psi (verified with a mechanical gage) it was this way when I bought it 7 months ago and I have been using it as a daily driver. It runs great so I have stopped worrying about it until I hear the bottom end knocking. I may pull the pan and replace the bearings and pump if I get the chance but I have heard of too many people doing this and still have low oil pressure. Low pressure is not a big concern IF (and it is a big IF) you are getting oil flow to all the bearings and lifters.
The thick oil that you are using may impede flow to where it is needed the most. 20-50 may be ok but I would drop the Lucus.

 

Use 10W-30 and a WIX filter. You don't need anything else.

13 PSI @ hot idle and 10 PSI for every 1000 RPM is acceptable.

Thicker oil does not compensate for or fix worn bearings.

Stock oil pump is all you need.

 

So how would I know if I had the bad cylinder head? Where would the serial number be so I can check it
I got the stock oil pump I plan on putting it in soon and see if that helps anything and where would I find that oil filter?

 

NAPA gold is the wix filter, or just ask. I did see posted "drivers side top edge" for that number, but I haven't even looked at mine!

If I had the pan off to deal with the pump, and was knocking, I'd plastigauge a few rods.

 

O'Reilly's has the actual WIX filter.

Some people say they can look through the oil fill hole in the valve cover towards the #3 valve area and see the crack (with a good flashlight I guess).

This is the 0331 head, which is weak in that area--a casting flaw.

 

So it doesn't say 0331 on any part of the head that you can see while it's on the motor

 

I just looked, mine has (2686(for the 87-90), right there, just back from the middle, back from the 4th head bolt on the drivers side. It's facing up.

I've also seen posted that "revised" 0331 heads have a "tupy" mark, actually somewhere INDIDE under the filler, maybe not easy to see. I've also seen posted that they can crack right there under the cap and you might see a thin line of coolant, or evidence that it has been leaking there, like whitish stuff maybe.

 

im going to check for that soon but right now i am in the middle of dropping the oil pan to change the oil pump back to stock. i have all the bolts out and the thing wont come off its like its hung up towards the rear main seal area. the starter and exhaust aint holding it back

 

I haven't done it. I gather from my book you might move the pan over to unbolt the pump. If you are not familiar with plastagauge, you might google it

 

im not doing the bottom end i am pretty sure the noise is from up top. i got tha pan out by removing the starter and just playing with the pan. now i am trying to figure out how to remove the pick up tube from the old pump and put it onto the new one. this is the first time i ever did an oil pump

 

Gotcha. Just that a new set of rod bearing inserts can be as low as $20, and they can be the first thing to go and finish an engine. I'm no help on the tube, you might bounce it off the guys up in "ask a question" thread.

 

will do thanks for the help

 

Since you have the pan off I would at least inspect the bearings with plastigage. Low oil pressure is usually from worn bearings but worn lifter bores can also cause it too.
If the bearings check out or if you have to replace them you will have peace of mind that the bottom end is good. Afterwards I would just drive it...my oil gage reading 0 (actually 4psi by mechanical gage) was worrisome but I've learned to live with it and it has not gotten any lower in 7 months and 7k miles I have no knocking.