Quick question regarding oil pressure

[blackhawk411]

98 XJ Auto NP231 120,xxx miles

I am very new to the whole Jeep thing so bare with me. I tried searching but did not come up with anything and I went through the whole 34pages of search results. I found one thread and had similar tendencies but no solution to it.

Anyway, is the needle supposed to drop when idling? It drops to 10ish and then as I give gas the pressure goes back to 40 range. I just got the oil changed about 200miles ago btw. Is this normal?

10 at idle 40 when driving.

 

[Firewater]

Manual says Minimum hot idle is 13psi. My '98 does drop to 10 with 10w/30 in traffic but will slowly climb up to about 20psi in park or nutral--that's what I do in stand-still traffic or at lights . . . I think its a good practice.

With 10w/40 I never drop below almost 20psi. What weight oil you using?

 

[blackhawk411]

10/30 i dont do my own oil change unfortunately. My apartment complex does not allow me to do so, I take it to the oil change shop. God knows what they use. "Penzoil" it might even be 1 part penzoil and like 3part crap

 

[crystalship1]

10 is a bit low.

I'd change the oil sender (AKA "oil switch") and see if the reading changes.

Good luck!! :thumbup:

 

[blackhawk411]

How hard is this...say compared to replacing spark plugs lol

 

[Standard]

That does seem pretty low.. my '99 with almost 99,000 on it sees about 25psi at idle and 40-50 driving around, after it's fully warmed up.

 

[JEFF]

How hard is this...say compared to replacing spark plugs lol

Real easy, you will need the special socket ($15.00) and a new sensor and that just threads into the oil filter adapter.

 

[twoksl2]

you can get at it with a combination wrench too. That's how I changed it. Don't remember the size off hand though.

 

[birchlakeXJ]

Oil pressure sending unit failure is quite common on the XJ. I would agree with replacing it. 10 minute job. If after replacing it, you're still running 10 at hot idle and you want to verify that the number is real, pull out that sending unit and replace it temporarily with a "mechanical oil pressure gauge". Compare your numbers.

 

[Comanchedude]

98 XJ Auto NP231 120,xxx miles

I am very new to the whole Jeep thing so bare with me. I tried searching but did not come up with anything and I went through the whole 34pages of search results. I found one thread and had similar tendencies but no solution to it.

Anyway, is the needle supposed to drop when idling? It drops to 10ish and then as I give gas the pressure goes back to 40 range. I just got the oil changed about 200miles ago btw. Is this normal?

10 at idle 40 when driving.

As noted above there things to check or replace for the gauge system. And the display system can read different on each ring. Now if you go that route and you still get the same reading don’t worry.
If you get 10psi at idle then you have oil pressure. There is no "requirement" of pressure for the Jeep 4.0, there are the normal expected reading like the 13psi at idle listed. And that reading was certainly observed on a new engine prolly with a direct gauge. If your oil pressure runs about 10 psi per 1k rpm, that has been and accepted amount of pressure throughout the automotive industry for most engine applications. Oil does not need to be under “hi” pressure to do its job is just need enough to stay on the reciprocating parts, so if you have pressure at all rpms your good

 

[mpncsnhs]

I totally agree with comanchedude, as long as you have oil pressure and your engine isnt knocking than dont worry about it, just add lucas when your oil gets changed. So many people are so quick to say "no oil pressure, time for an engine swap" as long as it runs good and you have oil pressure dont get to excited.