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just shoot me now.... low oil pressure

ybreal210

NAXJA Forum User
Location
Jackson, NJ
ok, someone just put a bullet in me now..... i have low oil pressure yet AGAIN........ i just finished putting a new high flow oil pump and a new rear main seal and a new oil pan gasket in the jeep this past sunday, had decent oil pressure at first, well for the first like 1/2 hour of driving...... but now im sitting at like 20psi when driving at full throttle.... this jeep used to sit at 40+ when at full throttle, im tryin to figure out other causes for this now lower oil pressure.... any advice would be great
 
What year is the patient?
 
If you are running a Fram filter, throw it in the trash.

A common problem is to get the pickup too close to the bottom of the pan, causing a restriction in flow.

Before you jump to any conclusions, get a manual gauge and hook it up. Way too many low oil pressure complaints are either bad gauges or bad senders.

Factory specs are like 13psi hot at an idle and 34 hot at cruise speed.
 
This is a stock engine? With how many miles on the clock? What was wrong with the original pump and why did you install a "high flow" pump? What was the oil pressure like with the stock pump? Low oil pressure, like the previous poster said, is often due to worn crank and rod bearings...tossing in a "hi-flo" pump isn't going to cure that. Does the new pump have an internal bypass that would prevent over pressurizing your filter during cold starts? If this bypass is stuck open, it would cause a low pressure condition.

mike
ooxj
 
the subject is an 89 xj limited, 86000 miles, i had a low oil pressure sit with the old pump checked out with a new sender, same thing, manual gauge said 4 psi at warm idle, when i had the pan off i did check the main bearings and they showed some sign of wear, but nothing that wouldnt be expected after 86000 miles on them, but no copper showing, the rod bearings i only pulled off one and checked it, it showed the same amount of wear as the mains..... i'm just puzzled as to why i still have this low pressure.... the new pump is a melling 20% over stock, looked the same as the oem with the bypass thing on the side of the pump, so im guesing it has the internal bypass as well... and no its not a fram, i had one on it and then read the horrors of them collapsing and took mine off and put on an STP filter..... just trying to figure out what else to check out before i go insane
 
If the rods and mains are good, then there are only a few things left. You could have a bad head gasket or shot cam bearings. Personally, if it is running fine, I would put some 20w50 in it and see what the pressure does. If it comes up to a reasonable number, I would just drive it. In school I drove a vehicle with half 90w for about 6 months till I had the $$$ and time to fix it.

At 4psi, are you getting lifter rattle? Instead of just looking at the bearings, I would do a Plastigauge test to be sure. You can always just replace the rod and main bearings without tearing down the engine as long as the crank looks smooth with no gauling.
 
Did you change the oil pressure sending unit?? If it's goofy, your readings will be way off. OR If it's not screwed in all the way.
 
guy at autozone messed up on my oil pressure sender. and got me a 60psi instead of 80. so when i see the gauge close to 80. its only near 60.
 
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