Oil Pressure Question

[97XJ Jeeper]

about half a quart if you are using factory size filter, if you are using a over sized filter 1 quart. just change the filter, start it up and then check the level, on the dip stick the add line is 1 quart low.

 

[lawsoncl]

how much oil will i lose when i take the filter off? I always do it when the oil is drained

Just what ever's in the filter.

 

[Ecomike]

Mine currently runs from 22 psi (HOT oil, 200 F, idling in park) to 60 psi (cold engine). I ran a thermal oil versus oil pressure test on mine and found that it takes up to 30 minutes idling with the A/C on, or a good 20 minute hard run on the freeway in the summer, to even get my oil up to 200 F. At 170 F I still get 30 PSI idling in park (about 550 rpm), but at 200 F it drops to 22 PSI idling in park. My oil takes 15 to 20 minutes longer than the coolant to reach peak temperatures. Oh, and at 150 F I still have 40 psi idling in park, even with my coolant already at 195 F.

I think it has a lot to do with the polymers they use nowdays in the multiviscosity oils too. There have been some discussions elsewhere about oil polymer additive shear problems causing low oil pressure.

I have 250,000 miles on mine ( but I have only owned it for 3 years, so I don't know the real engine mileage or complete history), running 20W50 plus 1 quart of Lucas. I also have a high flow oil pump and new crank bearings. If I run 10W30 it won't hold 10 PSI at 500 rpm in park with 200 F oil. The only bearings that were not checked recently were the cam bearings. The rest were OK. It does not use or burn oil.

Jeep spec is 13 psi minimum hot oil pressure in park at idle.

IIRC the oil pressure sensor is after the oil filter, so a clogged oil filter will show as a low hot oil, oil pressure, but does not show with cold oil.

 

[Cherokeekid88]

just went to wally world and picked up a mopar filter. Hope its the right size, they didnt have a listing for the mopar oil filter for an 88 but had one for a 91, so im guessing its the same. I compared it up next to a fram filter for my 88 and looks identical. So we will see what happens.

 

[RichP]

just went to wally world and picked up a mopar filter. Hope its the right size, they didnt have a listing for the mopar oil filter for an 88 but had one for a 91, so im guessing its the same. I compared it up next to a fram filter for my 88 and looks identical. So we will see what happens.

Keep an eye on the thread, at some point it changed sae to metric or the reverse, I don't remember which so if it does not thread you'll know why.

 

[cygnus58]

With a new sending unit, one bottle of STP red, a NAPA gold (WIx?) and a fresh change of 10-40 Valvoline my '88 runs 75 cold to 45 hot at idle.
So far no leaks and cranking to 5 degrees, this winter has been mild here..

 

[Ecomike]

Keep an eye on the thread, at some point it changed sae to metric or the reverse, I don't remember which so if it does not thread you'll know why.

Good catch, it changed in 91, the year the HO came out. 87 to 90 was metric, M20 X 1.5, the 91 was SAE, 3/4 X 16 TPI. Only difference is the thread. So he has the wrong filter for sure!

 

[Cherokeekid88]

crap! i knew i should have read the fine print! ok cool guys thanks for the heads up, glad i was able to find out this way other than halfway through the job.

 

[RichP]

crap! i knew i should have read the fine print! ok cool guys thanks for the heads up, glad i was able to find out this way other than halfway through the job.

Another thing to remember, before changing your tranny or transfer case fluid make sure you remove the FILL plug first BEFORE the drain plug, think about it.

 

[lawsoncl]

IIRC the oil pressure sensor is after the oil filter, so a clogged oil filter will show as a low hot oil, oil pressure, but does not show with cold oil.

Yup. The FSM lists plugged filter as a possible cause for low oil pressure.