I recently bought a jeep Cherokee with 84k miles on it and it runs and drives great but the only concern I have is that the gague keeps reading really low on my oil pressure while at idle. I tried putting thicker oil in it which actually seems like it runs better with that but the pressure gauge at idle still reads really low. Is this a common thing with the jeeps because I cant see how it would have low oil pressure at idle with a 40wt oil. The motor definitely likes the hdeo better the pcmo though it runs real smooth now. Thanks!
Jeep Cherokee Low oil pressure
- Thread starter 4x4chevydude
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How low is low?
The 4.0 likes a 40wt.
The 4.0 likes a 40wt.
First thing is to screw in a mechanical test gauge and verify that the dash gauge is accurate.
What does the inside of the motor look like? Is your oil cap dirty? Is there crud under the valve covers? Could be a dirty pick up screen. What did the oil look like at your last change?
What is the oil pressure reading hot?
The electronic gauges aren't always accurate. I'd make sure to get a mechanical gauge on there to verify what you're seeing on the gauge is correct.
The electronic gauges aren't always accurate. I'd make sure to get a mechanical gauge on there to verify what you're seeing on the gauge is correct.
+1 on electric sending units, they can fail. I believe mine did.
And reluctantly I have to admit that these "seem to like thicker oils" I do not know why.
And reluctantly I have to admit that these "seem to like thicker oils" I do not know why.
Pressure sender most likely going bad, common on the 4.0.
My 1998 Wrangler reads about 50 psig when the oil is warmed up completely running 10W40. It takes about 30 highway miles to get it up to temp. Warm idle is 25 to 30 psig.
Jeep oil pressure guages are known to be inaccurate an incorrect. If the lifters are not clicking it's probably okay just a bad sending unit
Sounds good I will have to verify Lowest I saw with the new thicker oil is prob 15 at an idle usually its 20ish or higher when I first start driving it.
Originally Posted By: 4x4chevydude
Sounds good I will have to verify Lowest I saw with the new thicker oil is prob 15 at an idle usually its 20ish or higher when I first start driving it.
the fsm states 11 psi hot idle is normal for the 4.0L.
Sounds good I will have to verify Lowest I saw with the new thicker oil is prob 15 at an idle usually its 20ish or higher when I first start driving it.
the fsm states 11 psi hot idle is normal for the 4.0L.
Originally Posted By: caravanmike
Originally Posted By: 4x4chevydude
Sounds good I will have to verify Lowest I saw with the new thicker oil is prob 15 at an idle usually its 20ish or higher when I first start driving it.
the fsm states 11 psi hot idle is normal for the 4.0L.
As caravanmike stated the min psi at idle is 11 by the FSM , Haynes states 13psi. At 84k I would suspect a oil sender on its way out. Replace the sender and refill with 30 wt . If pressure is still realy low most likely the oil pump needs to be replaced , although it 4.0L oil pumps tend to last longer. No need for 40 weight in a 4.0L it is a common misconception that the 4.0L does better on 40 weight oil , use the oil the engineers spec 10w-30.
Originally Posted By: 4x4chevydude
Sounds good I will have to verify Lowest I saw with the new thicker oil is prob 15 at an idle usually its 20ish or higher when I first start driving it.
the fsm states 11 psi hot idle is normal for the 4.0L.
As caravanmike stated the min psi at idle is 11 by the FSM , Haynes states 13psi. At 84k I would suspect a oil sender on its way out. Replace the sender and refill with 30 wt . If pressure is still realy low most likely the oil pump needs to be replaced , although it 4.0L oil pumps tend to last longer. No need for 40 weight in a 4.0L it is a common misconception that the 4.0L does better on 40 weight oil , use the oil the engineers spec 10w-30.
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