Hey guys,
I just started working on a new (to me) XJ and the oil pressure was at 0. i changed out the pressure sensor and connector and got a better reading. When i first start it up i have 45 psi, but as it warms up it drops to 10 psi at idle and 20-25 at 60 mph? I am going to replace the oil pump and check out the rod bearing while im under there. Any other thoughts? I appreciate the feed back!

 

Check it with a mechanical gauge to make sure that gauge is not wrong also.

 

@country2 i did the gauge is reading correctly, it just seems to be slowly loosing pressure. 15-20 mins in i am at 20-25 psi at 55-60 mph

 

How old is the oil and what weight?

 

@TrailerTrash its 10w30 just replaced it a few days ago. jeep has 188,000 on it

 

I am having the same issue. Update us when you get it sorted out.

 

Try 15W40 diesel oil and a Motorcraft FL1A filter.

 

im planning on working on it in the next couple days, i had to drive it to work today and 65-70 i had 20 pounds of oil pressure? Think that is okay to drive the 45 mins to and from work until i can work on it?

 

20 psi is within spec.

 

Is it spec in that RPM range?

I seem to remember minimum numbers being 13psi at idle and 27psi at 1800rpm

 

that is what i'm wondering? 20 psi at 65 with 2000 rpm si what i am running now.

 

Not less than 13 psi at HOT idle and Between 37-75 psi over 1600 rpms is what I always thought. Is it ticking/noisey?

 

Switch to Rotella T6 5W-40 or 15W-40 depending on your climate and a good quality WIX oil filter. The thicker oil will raise the mean oil pressure by approximately 10psi across the rpm range and Rotella contains the highest level of ZDDP currently on the market. Low oil pressure on the 4.0 is a common issue/concern and while you can replace the oil pump, try switching oil first.

 

Also keep in mind that replacing the oil pump will not fix the tolerance issue that is the typical cause of low oil pressure.

 

I’ll change the oil and change the oils pump since I already got it lol what oil is good for colder climates? I am in northern Wisconsin.