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  #1  
Old June 19th, 2017, 17:56
eightsevenzero eightsevenzero is offline
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Low oil pressure (16 psi) at warm idle

I've had quite a few XJ's but the 97 I just picked up (147k) is the only one I've had that shows 16 PSI at warm idle. At 1600 rpm it jumps right up to 40-45 PSI and operates solidly at 40-45 PSI at anything but idle. Just changed oil (Mobil 1 synthetic 10w-30) and filter just to be sure it wasn't a faulty filter. I know I should do a mechanical gauge check just to be sure but assuming it's right is 16 at idle is cause for concern? Apart from a steady miss at idle (I posted another thread about this) it runs great.

Last edited by eightsevenzero; June 19th, 2017 at 18:08.
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Old June 19th, 2017, 18:02
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Re: Low oil pressure (16 psi) at warm idle

10-25 psi at warm idle is normal. No worries.
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Old June 19th, 2017, 18:08
eightsevenzero eightsevenzero is offline
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Re: Low oil pressure (16 psi) at warm idle

Gotcha. Curious, what would cause my last XJ, a '99 with 187k to have higher oil pressure at idle than this one with 147K?
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Old June 19th, 2017, 18:28
blakews2217 blakews2217 is offline
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Low oil pressure (16 psi) at warm idle

I've never had the issue of low oil pressure at idle without engine damage. I've got main bearings that got eaten alive during break in and I hold 3-7 hot at all rpm and 40 dead cold. It progresses down.


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Old June 20th, 2017, 07:24
ReverendOD ReverendOD is offline
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Re: Low oil pressure (16 psi) at warm idle

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Originally Posted by blakews2217 View Post
I've never had the issue of low oil pressure at idle without engine damage. I've got main bearings that got eaten alive during break in and I hold 3-7 hot at all rpm and 40 dead cold. It progresses down.


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Same here. I've run 3psi hot idle for over 100k miles

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Old June 20th, 2017, 07:36
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Re: Low oil pressure (16 psi) at warm idle

10 is the factory spec.
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Old June 20th, 2017, 08:33
md21722 md21722 is offline
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Re: Low oil pressure (16 psi) at warm idle

Quote:
Originally Posted by eightsevenzero View Post
Gotcha. Curious, what would cause my last XJ, a '99 with 187k to have higher oil pressure at idle than this one with 147K?
Condition of engine bearings, oil pump, and sending unit.
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Old June 20th, 2017, 09:20
dan1977p dan1977p is offline
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Re: Low oil pressure (16 psi) at warm idle

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Condition of engine bearings, oil pump, and sending unit.
Crappy restrictive/dirty oil filter as well
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Old June 20th, 2017, 10:43
blakews2217 blakews2217 is offline
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Low oil pressure (16 psi) at warm idle

Quote:
Originally Posted by md21722 View Post
Condition of engine bearings, oil pump, and sending unit.


Exactly. I have worn out main bearings. Great cold. Crappy hot



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Old June 20th, 2017, 12:58
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Re: Low oil pressure (16 psi) at warm idle

It just means you need thicker oil.
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Old June 20th, 2017, 15:15
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Re: Low oil pressure (16 psi) at warm idle

Quote:
Originally Posted by eightsevenzero View Post
Gotcha. Curious, what would cause my last XJ, a '99 with 187k to have higher oil pressure at idle than this one with 147K?
The oil gauge is mostly an indicator, not a calibrated measuring device. The pressure sensor may be off slightly, or the motor simply has better or worse oil pressure than the next 4.0L. Some Jeeps have a bit higher oil pressure, and some a bit lower, neither will explode anytime soon.

Lots of people have driven lots of miles with less than perfect oil pressure.
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Old June 24th, 2017, 09:57
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Re: Low oil pressure (16 psi) at warm idle

My 2001 has 10 at idle, 50 at 50mph. Gradually drops to 40 at 50 mph. Thats where it stays until I change the oil/filter, it then goes back to 50 at 50. Been that way since the start.
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