no oil pressure

[Jennifer Knowlton]

2000 Jeep Cherokee 4.0

start engine have 40lbs of oil pressure... engine temp warms up oil pressure goes down after 10 minutes of running oil pressure goes all the way to zero. though engine makes no noise one would expect from having no oil pressure. when driving it have around 20+\- lbs

i have changed to a mechanical oil pressure gauge, changed the oil pump, changed the mains, rod bearings, changed the o-rings behind the oil filter and the oil pressure sending unit.


i have to missing something..

 

[greg92jeepxj]

Hi Jennifer . Welcome to Jeepz.com :welcome: earlier , I posted what you had already done , to replace the o-rings on the oil filter sending unit adapter , but had deleted it since it was repetitive and an embarrassing error on my part. You've already done all the things I am aware of , above and beyond , in regards to low oil pressure . Sad to say , I cannot think of anything else , hoping another member will come to your rescue. We truly have good people in terms of diagnostic and repair and I believe someone will have an answer to this problem. Hang in there .
Would like to thank you on behalf of Jeepz.com for your membership and thank you once again for choosing us . Thank you . Greg

 

[uberxj92]

Hi all. Ok Jennifer you unfortunately have the 0331 head. Used them in 2000-2001 on xjs. These heads crack if they get their feelings hurt.
Low oil pressure is a symptom if that issue. Let's hope its not that .
Cam bearings will affect oil pressure as well.
The xj 4.0 sits a little low in the back. It had a tendency to pool oil in the rear if the head causing sludge. That'll contribute to. If you use a Tcase drop that makes it worse.
Oil filters are not created equal either. We use mopars at our machine shop.

You have overhauled her well. So I'm thinking try a different filter.
Maybe flush the engine with Lucas or a little diesel.
How does it run otherwise? Any performance issues like weak acceleration or anything like that? Does it run warmer than 210?
Did you make sure that all if the mains were installed right I mean the oil journals lined up?

 

[carnuck]

What oil? What brand filter? (if orange, change it first) In fact, if it is, I would consider taking the filter adapter off and reverse blowing pressure through the sender fitting to see if there is a clog in the gallery. Aside from that, cam bearings or you didn't clean out the oil pump screen.