• 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.

oil pressure gage

Spec is minimum 13 psi at hot idle which means yours is showing pretty close to the minimum.

Many times the oil pressure sending units start reading low or go out altogether. I'd suggest putting a mechanical gauge on it and see if the dash gauge is the same. If the mechanical gauge reads higher, then you could probably fix your dash gauge by replacing the oil pressure sending unit. Dealer sensors work best.
 
Driving several years with a XJ gage cluster of the warning lamp style, I only once had the lamp illuminate for oil. Replaced the sensor. Should your oil psi go below 10psi at any point whilst the engine runs, It'd be an idea to have it checked. Do you have oil under your XJ on the ground?:eek:wl:
 
md21722 said:
Spec is minimum 13 psi at hot idle which means yours is showing pretty close to the minimum.

Many times the oil pressure sending units start reading low or go out altogether. I'd suggest putting a mechanical gauge on it and see if the dash gauge is the same. If the mechanical gauge reads higher, then you could probably fix your dash gauge by replacing the oil pressure sending unit. Dealer sensors work best.
Click to expand...



When I press the gas to go it stays at 40 when I let go of the gas it goes back down
 
10-15 psi at warm idle and 35-45+ psi at 55 mph is normal. Oil pressure variations are directly related to engine rpms.

195*-210* is normal.

Many 4.0 have driven very many miles with less that normal oil pressures.
 
mechbullxj said:
Driving several years with a XJ gage cluster of the warning lamp style, I only once had the lamp illuminate for oil. Replaced the sensor. Should your oil psi go below 10psi at any point whilst the engine runs, It'd be an idea to have it checked. Do you have oil under your XJ on the ground?:eek:wl:
Click to expand...


I thought maybe I had an oil leak but I put a cardboard under the car and there was no oil on the Cardboard the next day.
 
When was the oil changed last? What weight? What filter? In my case a different filter (NAPA, Wix) made a big difference in my gauge reading.

15 at hot idle and 40 ish at 1500 and up
to
20 at hot idle and 60 at 1500 and up.

I've also had two sending units go out on me on two separate Jeeps in 10 years and both times, the gauge pegged to 80+ instead of just giving me a low or bad reading
 
ParadiseXJ said:
When was the oil changed last? What weight? What filter? In my case a different filter (NAPA, Wix) made a big difference in my gauge reading.

15 at hot idle and 40 ish at 1500 and up
to
20 at hot idle and 60 at 1500 and up.

I've also had two sending units go out on me on two separate Jeeps in 10 years and both times, the gauge pegged to 80+ instead of just giving me a low or bad reading
Click to expand...


Well my brother in law works at toyota I go to his job at least 1 to 2 times a month. Every time I go I change the oil but I don't change the filter all the time. The weight of the oil at toyota is 5-20 my jeep has 135xxx miles.
 
5w-20 was never specified for the 4.0

5w-30/10w-30 are what is specified. Some people prefer to use thicker oil such as 5w-40.

I have had two sending units read low over time.
 
You need to confirm your pressure with a mechanical gauge. And you need to run either 30 or 40 weight oil vs 20

Also, what other have said. Filter quality is important. Fram fails. Wix or better.
 
I changed my oil and filter today and my idling pressure went from 25 before to 50 psi after. This has always been the case when I change the filter. It's been only 4000 miles since the last change and more than 3000 of that is highway miles. Change your oil and filter and then let us know what happens.
 
5 20 is too thin for this motor and you need to change the filters every time on these older engines since there is typically a lot more blow by than on a new engine. For 20 dollars a year you can't afford not to.
 
2X_01_Jeeps said:
Wrong weight oil.
10W-30.

Or bad oil pressure sender.
Click to expand...
Third.
Late model Jeeps and Toyotas may specify 5W-20 because the engines have tighter tolerances. But your Jeep specifies 10W-30 because the engine doesn't have as tight of tolerances. Use the oil specified.

Running thicker 10W-30 in a newer Jeep or Toyota engine designed for 5W-20 will probably result in restricted oil flow and show much higher oil pressure.

Running thinner 5W-20 in a older Jeep engine designed for 10W-30 will probably result in oil flowing through the bearings too quickly and show lower oil pressures. Which is what you're seeing.

Check your O.M., most state it is ok for the low oil pressure light to come on during hot idle in gear, i.e. stopped at a light, but it should go out as soon as step on the gas. That is the absolute minimal oil pressure acceptable and NOT cause engine damage, the oil pressure should be and is usually higher at all points. Going back to the specified oil should raise the pressure some, but you did your engine no favors running an oil thinner than specified, you may have created additional wear and tear on the motor.
 
You must log in or register to reply here.

Similar threads

A
1987 4.0 oil pressure problem
Replies
1
Views
1K
RCP Phx
R
Z
RENIX fuel delivery questions
Replies
4
Views
338
Ecomike
Ecomike
O
A/C Freon question
Replies
1
Views
1K
Saudade
Saudade
O
0331 Strikes Again...?
Replies
11
Views
303
Ol Blue
O
M
Oil pressure question
2
Replies
26
Views
3K
Money_Pit_Incoming
M
Back
Top