99 WJ 4.0 204k idle 10psi oil pressure - JeepForum.com
 
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post #1 of 8 Old 05-03-2021, 05:33 PM Thread Starter
tsetsaf
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99 WJ 4.0 204k idle 10psi oil pressure

As the title describes. Bought as a mechanic special. Great jeep overall. Very clean and well maintained. No valve train or other noises.

Previous owner sold because the stock pressure gauge was tripping the gauge light. I installed a manual gauge and oil pressure drops to 10psi once really warm and driven.

Book says 13 psi for low end. I plan to pull the motor but want to push it a couple months before doing so. Oil pressure is fine with some throttle.

Changed oil to 5w40 plus Lucas oil stabilizer.

I have read many of the other posts on this topic and appreciate the combined wisdom hear within.

If you were to take a bet... how many more miles will I get out of this motor?

What are your thoughts?

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post #2 of 8 Old 05-03-2021, 07:06 PM
jtec
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try some hail marys, yes to the lucas, and 5w40, maybe a quality filter, add some RISOLONE maybe it frees up a oil bypass relief, let us know, but plan on a pump, gather the parts get a good work place pick the time - you don't need a hi volume.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 8 Old 05-03-2021, 07:47 PM
Caish
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Low oil pressure at idle most of the time can be traced to worn cam bearings.
My old 258 in the YJ/CJ hybrid aka Halfbreed has 5 psi or less at idle, then lifters start ticking, but running down the road its 25 psi.
Generally as a rule you need 10 psi for every 1000 RPM...

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post #4 of 8 Old 05-03-2021, 10:02 PM Thread Starter
tsetsaf
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Quote:
Originally Posted by Caish View Post
Low oil pressure at idle most of the time can be traced to worn cam bearings.
My old 258 in the YJ/CJ hybrid aka Halfbreed has 5 psi or less at idle, then lifters start ticking, but running down the road its 25 psi.
Generally as a rule you need 10 psi for every 1000 RPM...
So is it simply a cause for ticking or will it kill the motor?
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post #5 of 8 Old 05-04-2021, 04:30 PM
Caish
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Quote:
Originally Posted by tsetsaf View Post
So is it simply a cause for ticking or will it kill the motor?
IF oil pressure is low enough the lifters are ticking, I would be concerned.
I would pull the oil pan and drop a rod cap, and Main Cap inspect the bearings, Not hard to change them, could get it back up, I would also check the clearance in the oil pump, could be just a weak, pump.
200k on a 4.0 if had regular oil changes wouldn't think bearings to be shot.
I have another question, when cold start, how bad does it rattle and how long before it quiets down?
But still thinking cam bearings.....

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post #6 of 8 Old 05-04-2021, 05:03 PM
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I would run 15w40 in a loose engine. If I was still nervous I would run 50 wt racing oil until tear down time.
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post #7 of 8 Old 05-04-2021, 08:40 PM
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Quote:
Originally Posted by snowbuggy View Post
I would run 15w40 in a loose engine. If I was still nervous I would run 50 wt racing oil until tear down time.

this is right. if it was my motor, and i had oil pressure that low, i'd be running synthetic 30 weight, at the minimum. i'd put a good filter in it, as well, and i'd consider doing a flush with chemicals, before that 30 weight oil change. 50w works in the summer, it will be like tar come january though.

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post #8 of 8 Old 05-04-2021, 10:40 PM Thread Starter
tsetsaf
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Quote:
Originally Posted by Caish View Post
Quote:
Originally Posted by tsetsaf View Post
So is it simply a cause for ticking or will it kill the motor?
IF oil pressure is low enough the lifters are ticking, I would be concerned.
I would pull the oil pan and drop a rod cap, and Main Cap inspect the bearings, Not hard to change them, could get it back up, I would also check the clearance in the oil pump, could be just a weak, pump.
200k on a 4.0 if had regular oil changes wouldn't think bearings to be shot.
I have another question, when cold start, how bad does it rattle and how long before it quiets down?
But still thinking cam bearings.....
Fires right up and pressure immediately goes to 45 psi. There is a minor mechanical sound but nothing pronounced and immediately gone when the pressure rises.

Thanks for the feedback everyone. I will take it easy until I can drop the pan. Will report back.
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