• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Low Oil Pressure, not the sending unit, should I worry?

Mastodon

NAXJA Forum User
Location
Northern VA
This is a 2000 XJ 4.0 I6 ~106,xxx miles on it.

The last 2 weeks my oil pressure has been dropping once the temperature reads ~210 degrees.

It will run at about 20-30 psi in top gear when cruising and drop down to almost zero at idle.

I also notice more heat coming through the instrument panels and cd player after extended driving now that this happens.

Took it to a mechanic to see if it was the sending unit, he said it was fine and just engine wear.

Engine appears to be running quite healthy, just had a new set of plugs and coil pack installed and there are no unusual sounds of signs of damage coming from the engine. Oil has changed regularly since I've owned it and is a little under 3,000 miles right now.

Should I still be concerned? Any guess as to how many more miles I can expect out of it (I was hoping for the legendary ~300,000 miles) anything else I could do to ease this? I make frequent long car rides (anywhere from 2-8 hours up and down the east coast) should I keep those to a minimum?

Thanks in advance for your responses.
 
Could be wear, could be the oil pump, could be a clogged screen on the oil pump, could be a dirty motor. If it were me, I'd consider dropping the pan, and checking/cleaning the oil pump and screen, and popping the valve cover to check for crud.

What weight of oil are you running? A bandaid fix would be to use a heavier oil. 15w40 or 20w50 seems to be popular.
 
I don't see any actual "confirmation" of oil pressure numbers. You really can't trust your factory gauge at this point without confirming it. Getting believable data is what really needs to be done in order to see where you are at.

Unless the technican you took it to temporarily installed a "mechanical" oil pressure gauge to give you a true number, that is what you should do. It only takes a few minutes. The gauge installs where the sending unit for oil pressure currently sits. Some big box parts stores rent this mechanical gauge for a few bucks.

Without confirmed oil pressure numbers you might be chasing your tail when you don't need to be. Post back your confirmed oil pressure readings (cold, hot, etc) here for comment. 13 psi at hot idle is what Jeep says is a minimum number for the 4.0, but I have seen more than a few guys run at 10 psi hot idle for quite some time with no issue.
 
Last edited:
"Mechanic says" is not a reliable test. And don't worry about the extended trips. Most of the wear in an engine is at start-up. And that is a good reason why the thicker oil bandaid can be a problem.
 
Beg/borrow/rent/steal(?) a mechanical oil pressure gauge and confirm the oil pressure, as the others have recommended.

What oil viscosity are you running? Brand of oil filter? What is the maintenance history of the engine?
 
Thanks for the replies. I'll post back once I can get some numbers, I added some STP to the oil in the meantime for the sake of it.

Edit: Oil viscosity is 10W-30, filter brand is Purolator.
 
Back
Top