Continuing oil pressure issue with 4.0

Lorado

Lorado

Member
Joined
Aug 27, 2022
Messages
26
Location
Iowa
Hi all
A little over a year ago I bought a 97 tj sport 4.0 manual. It currently has 135k on it. When I first got it I noticed low oil pressure when warm so I started with the pressure sender, then a high flow oil pump. Then this past weekend finally got around to main bearings and then a mechanical gauge. Still after about 15 miles the pressure drops from 50 psi to 25psi and at idle at stop lights it drops to near 0. Idk where to look next. Has anyone else conquered this issue?
 
JKP said:
If you did the mains and rod bearings, only thing left is the cam bearings.
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I only did the mains. Was going off of a family mechanics advice to start with the mains. Kinda kicking myself for not doing rod bearings while having it apart.
 
Lorado said:
Are undersized bearings for a worn engine or a factory deviation?
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Undersized bearings are typically used as a solution for worn engine components. When an engine experiences wear, particularly on the crankshaft or connecting rod journals, it can cause the bearing clearances to be outside of the acceptable range. In such cases, undersized bearings can be used to compensate for the wear and restore proper oil clearance. Undersized bearings are not a factory deviation; they are a remedy for excessive wear in an engine.
 
Given the lengths that I have gone to with little change in oil pressure I'd imagine undersized bearings might be called for then?
 
Have you used a good mechanical oil guage screwed into the sender port to verify the issue isn't electrical?
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My 97 reads a false low after a new mopar sender on a motor with 20k miles. I'll diagnose it some day
 
I have that exact gauge installed. Maybe a different brand but copper tubing and all. I had the same thought that maybe it was a faulty factory gauge.
 
Try some plastiguage on the rods. That way you know if theres an issue before rolling in bearings. You could try it on the mains too so you know what you have before going after removing the engine and cam bearings
 
Rickyd said:
Try some plastiguage on the rods. That way you know if theres an issue before rolling in bearings. You could try it on the mains too so you know what you have before going after removing the engine and cam bearings
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Ill have to give that a try
 
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