Renix Oil pressure range

AwesomeXJ · Mar 16, 2011

Just wondering what the normal operating oil pressure range is for a 1990 renix xj.

I've tried searching but I don't have hours to comb through every post that has the word oil in it.

Thanks.

kastein · Mar 16, 2011

About 40psi hot running temp, and 20psi idle. Depends on how worn your motor is.

1990JEEPXJ · Mar 16, 2011

x2. 20 and 40 are good numbers to be at when hot.

xjtrailrider · Mar 16, 2011

75 cold, 35 hot. Mine is a brand new motor though, Rotella 10w-30

AwesomeXJ · Mar 16, 2011

UPDATE: Talked to the lead mechanic at my local JEEP dealership. He said for a 1990 4.0l renix it should be 25cold 10hot.

Firyls · Mar 16, 2011

My Original 1989 Owners manual says 20-60psi for normal city driving, 45-60psi for HWY driving, and 13psi hot engine at idle is satisfactory.

And noted at the end "Consistent lower readings indicate possible malfunction"

1990JEEPXJ · Mar 16, 2011

aaron barnes said:
UPDATE: Talked to the lead mechanic at my local JEEP dealership. He said for a 1990 4.0l renix it should be 25cold 10hot.

10 is too low, 13 is the minimum. mine is about 40 cold and 20 hot at idle and nearly 200k miles. what is yours running at?

lawsoncl · Mar 17, 2011

Of course, take the dash guage with a very large grain of salt. It's not terribly accurate and if you're concerned about oil pressure, use a mechanical guage to verify it.

The FSM lists the minimum pressure at 600 rpm as 13psi, and 37-75psi above 1600 rpm.

PhotographerMike · Mar 17, 2011

A couple of things. 1) search within NAXJA

needs 4 characters to work, try oil*

Oil pressure gauge tells if the engine is in normal range, if it suddenly changes radically, something's wrong.

AwesomeXJ · Mar 17, 2011

Gauge reads 10 while driving around and 30-40 when cold

ParadiseXJ · Mar 17, 2011

aaron barnes said:
UPDATE: Talked to the lead mechanic at my local JEEP dealership. He said for a 1990 4.0l renix it should be 25cold 10hot.

Did the lead mechanic ever read the FSM??

lawsoncl said:
...use a mechanical guage to verify it.

The FSM lists the minimum pressure at 600 rpm as 13psi, and 37-75psi above 1600 rpm.

Verify with a mechanical gauge...then spend $15 on another sender.

If it all indicates that your pressure is indeed to low, you may need a new oil pump.

I have 2 Renix Jeeps and I think I might flip out a little if my pressure was ~10 psi.

kastein · Mar 17, 2011

Don't sweat it too much... I have run my MJ's motor completely out of oil at least a half dozen times (it leaks like a sieve and I forget to fill it occasionally) and it continues to run great. I've had it on the rev limiter trying to get up a snowy hill with the lifters sounding like a diesel freight train and the oil pressure etc bounce right back afterwards, has never given me a bit of trouble. And it has 230 thousand miles on it.

If mine can survive my treatment, yours running a little on the low pressure side will last forever.

Glenn B · Mar 17, 2011

My 89 has 40psi idle at temp.... city driving or pounding it through the sand. Other than that, the stock guage is pegged. I use it as just an indicator or normal/abnormal.

An old school rule of thumb is 10 psi oil pressure for every 1000 rpm. 10 psi at idle would not make me happy, but is also enough oil pressure for the engine to live.

1987Comanche · Mar 17, 2011

I'd be inclined to believe the Jeep mechanic for the min oil pressure numbers. I have 40PSI cold, 10PSI hot idle, and 25PSI hot at highway speeds (2200RPM). I'd like higher oil pressure and I verified the dash cluster with a mechanical gauge. As it is I try not to rev her too high, keep the oil clean, and keep on driving.

cruiser54 · Mar 17, 2011

1987Comanche said:
I'd be inclined to believe the Jeep mechanic for the min oil pressure numbers. I have 40PSI cold, 10PSI hot idle, and 25PSI hot at highway speeds (2200RPM). I'd like higher oil pressure and I verified the dash cluster with a mechanical gauge. As it is I try not to rev her too high, keep the oil clean, and keep on driving.

I'd be inclined to believe that your oil pressure is low being that 3 of my Jeeps run 40+ at highway speeds and 20 at idle hot. I'll get 60 cold at idle.

birchlakeXJ · Mar 17, 2011

Don't guess.

Buy or rent a mechanical oil pressure gauge. Temporarily install it where the oil pressure sending unit currently resides. Post back what you find.

Good data = Good Decisions.

joe_peters · Mar 25, 2011

birchlakeXJ said:
Don't guess.

Buy or rent a mechanical oil pressure gauge. Temporarily install it where the oil pressure sending unit currently resides. Post back what you find.

Good data = Good Decisions.

DO THIS.

joe_peters · Mar 25, 2011

Question: What is the correct oil pressure in a 1990 Renix XJ.

4.0 engine: 13 psi @ idle; 37-75 psi @ 1600 rpms; pressure relief set to 75 psi.

2.5 engine: 25-35 psi @ idle speed (800 rpm); 37-75 psi @ 1600 rpms; pressure relief set to 75 psi.

Feel free to share that info with the "lead" tech--this information is located in the FSM at the end of each engine section.

RULE OF THUMB with the old farts is 10 psi @ idle; 10 psi per 1000 of rpms.

Good luck.

JohnX · Mar 25, 2011

Rule of thumb for ANY automotive gas engine.

1 psi minimum for every 100 rpm when hot.

7psi at idle hot, should not cause any damage. 30 psi cruising on the highway, again should not hurt anything.

I know what the book says...but Joe is right on the money here.

Renix Oil pressure range

AwesomeXJ

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kastein

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1990JEEPXJ

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AwesomeXJ

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