XJ Hero

I have a 99 XJ, 187k. I just recently replaced my oil pressure sensor , about 2-3 weeks ago due to gauge maxing out with ignition on. Just under a week ago I did an oil/filter change. Within a day or so my gauge starting reading higher mostly at cruising speeds. Usual reading on stock sensor was around 50 cruising at 1700rpm. Now its staying around 60psi with peaks to 65-70psi. Its not constant at 60-70, seems to float up then slowly come back down.

When I drained the oil out it seemed fine, no serious sludge or anything( I cut the filter to check that too and that was fairly clean as well), but it seems like theres something partially clogging the system now and bringing that pressure up. Also thought it could just be the sensor, heard that alot of aftermarket brand sensors have accuracy issues. Didnt hook up a manual pressure gauge, plan on it, just looking for any more info in the meantime. Also, does anyone know the actual max and min oil pressures limits for the 4.0L engine at idle, or a set rpm? Wanted to at least know if my numbers were in factory specs. Thanks

playbass

The min is 13 psi at hot idle. When you are above 1700rpms it should be 37 psi min and 70 psi max.

tjwalker

It indeed is not unusual for aftermarket oil pressure sending units to fail prematurely or be inaccurate.

It is why I always recommend purchasing them directly from Jeep. Well worth the extra $20 or so.

Verify if you like with a mechanical oil pressure gauge. Or just pick up a Mopar sending unit.

dazrox88

mine does the same thing, i never worried about it, like playbass said, 70psi max and i was always right around 65-70psi
what kind of filter do you run btw? not orange with some bed-liner on it is it?

RTorrez1

Like walker said it is very common to get a bad sending unit. Also it is possible that you may have hit the new sending unit and not know it. they are pretty fragile even if it is on a 4x4. You would think that they would make them more durable.

CCKen

75 psi is the OP relief valve setting. My '99 FSM says @ 1600 RPM & higher, 37 to 75 psi.

XJ Hero

Thanks for all the quick responses guys, pretty much what I thought. I actually work at CAP, so i got the sensor real cheap with my discount, otherwise I would have gone to Jeep for one.
And yes, I use an orange bed-lined FRAM....after throwing that on a few times kinda want to try another brand, just to see any difference. I have heard bad things about FRAMS on Jeeps, any recomendations on filter type?
P.S. I always change at 3000-3500K.

I also heard that those units can be very fragile...I was very delicate putting the new one on, and anytime I go around it to change the filter.

The Rooster

Yes a wix oil filter or napa gold... The napa is made by wix if you carry wix at cap then try a wix

BigStrongVikingBaby

Wix is expensive ~ $7 but high quality. I like Bosch and AC delco; good quality and price

arorton

I use a mopar filter to try to keep my oil pressure up, not exactly what you're looking for, but I feel like mine runs stronger with a mopar than anything else

XJ Hero

Alright, thanks guys, ill have to try a Wix next.