Should my oil pressure be doing this?

[Fergie]

When my Jeep is warmed up, the oil pressure gauge has been working kind of funny. At idle, or no gas, the pressure is right around 40psi. When I step on the gas, it goes to around 60-80psi, depending on how hard I am accelerating. What is the deal?

The Jeep is a 1995, 4.0L, AW-4, 231. I just recently did a full gauge swap, but I don't think that changing the oil pressure sensor would have made this happen. Please help me out, as I don't know if this is serious or not. The oil level is fine, and the vehicle is running properly. Thanks in advance.

Fergie

 

[PaulJ]

Sounds normal.

 

[imma honky]

If his is normal, then mine isn't?
braking = lowers pressure (about 25)
accel = 45
??

 

[juicexj24]

Ya I would say to have that checked out. Mine goes to 40 and stays there with the gas pedel on, at idle it goes down to 20. It shouldn't be going to 80, you might have over filled the oil. check the dip stick first and make sure it's not to high. Than check the wiring of the gauges. Juice

 

[Mikel]

My 140K mile 4.0 gets 20psi at idle and 45 at 2000rpm when warm.

 

[seanR]

I have found what work best for me is, In the summer I run Rotella 15/40 and in the winter I run 10/30. Now that I have a garage, I might try the 15/40 year 'round. I just don't like the 'dry starts' from the heavy oil in the sub-zero winters.

 

[Fergie]

Well I just changed my oil and plugs tonight, so we'll see how that goes. I put 10-30 in it this time, instead of 10-40. I payed closer attn to the gauge and it only goes to 60 when I step on it. Time will tell if there is an actual problem.

Fergie

 

[imma honky]

Same here, 10-30 High mile oil

 

[Eagle]

High oil pressure is usually considered a virtue, not a problem.

The factory spec is 13 psi minimum at 650 RPM idle, and 37 to 75 psi above 1600 RPM.

The oil pump is driven by the camshaft, and therefore the speed of rotation varies with the engine speed. It is normal for the idle oil pressure to be lower than the highway oil pressure -- generally by approximately a factor of two.

Oil is also thicker when cold, and oil pressures (both idle and running) will be higher when cold than after the engine warms up. Most newer XJs I've driven seem to idle at about 30 psi and run at 50 to 55 psi on the highway. In my '88s I run Castrol full synthetic 5W50. The XJ with high mileage idles at 25 psi and runs at between 40 and 45 -- the MJ (with much less mileage) idles at 35 psi and runs at 60. Both are within spec and I don't consider either to be a "problem" (although I wish the XJ pressure were higher -- I should have switched to synth long before I did).

 

[kccherokees]

I have had the same prob, just did an engine rebuild and at idle its like at 18-19 no idea why! I did put in a comp cam, would that have anything to do with it? Thanks

Chris

 

[JEONLYEP]

me too

Only mine doesn't seem to do it all the time. It's max is around 80 at heavy acceleration. 40 down the hiway. 30 Idle. if it's not peaking with acceleration, it stays around the 40 mark and the hiway and idle numbers are the same as stated earlier.

 

[Eagle]

Re: me too

Only mine doesn't seem to do it all the time. It's max is around 80 at heavy acceleration. 40 down the hiway. 30 Idle. if it's not peaking with acceleration, it stays around the 40 mark and the hiway and idle numbers are the same as stated earlier.

Let's define terms here.

Acceleration should not affect oil pressure. What affects it is engine RPM. When you say "heavy acceleration," do you mean just going from 2000 RPM to 2500 RPM with your foot to the floor, or do really mean that you're running the engine up near the 5000 RPM redline?

Some people claim that oil pressure increases 10 psi for every 1000 RPM. I haven't seen that with my Jeeps, but I'm an olde phart and I never go above 3000 or maybe 3500 RPM so I wouldn't notice much change in mine anyway.

It's also possible that your sender unit isn't accurate. The oil pump has a relief spring that's supposed to be set for 75 psi, so in theory it should be impossible for you to be seeing 80 psi on your gauge. However, I doubt the relief spring is perfectly calibrated, and I'm sure the sending unit isn't 100% accurate.

Bottom line -- if it's within the specified range during normal driving, I don't see any reason to worry.

 

[OT]

MIne does the same thing. It began on the drive to Moab in April and has done it since. I've done 3 oil changes since then and it only seems to get normal readings right after the change. However, in all this time I havent noticed any change in performance or smoothness. I've just chalked it up to possibly a bad pressure sending unit or a cRaZy nuance.

 

[June]

Check your oil pressure sending unit. Mine did the exact same thing a while ago just before it died. I replaced it and now it's doing it again. Go figure.

 

[JEONLYEP]

Re: Re: me too

Let's define terms here.

Acceleration should not affect oil pressure. What affects it is engine RPM. When you say "heavy acceleration," do you mean just going from 2000 RPM to 2500 RPM with your foot to the floor, or do really mean that you're running the engine up near the 5000 RPM redline?

Some people claim that oil pressure increases 10 psi for every 1000 RPM. I haven't seen that with my Jeeps, but I'm an olde phart and I never go above 3000 or maybe 3500 RPM so I wouldn't notice much change in mine anyway.

Hard accel for me is getting close to 3500. Am thinking there is a blockage in pcv elbow (seen in a different thread) oil leak at rear main seems worse when oil pressure is showing higher.

Any of that make sense?

Thanks.

 

[OT]

Am thinking there is a blockage in pcv elbow (seen in a different thread) oil leak at rear main seems worse when oil pressure is showing higher.

I think it has less to do with high pressure and more to do with excessive blowby. Better ventilation in crankcase and less blowby out the rear main.

 

[JEONLYEP]

Okay

Maybe screwy pressure sending unit and a blocked pcv elbow? Or a bad rear seal.

All I really know is there is an oil leak at the seal and the pressure according to the guage moves around. But it's never goes low, so I don't worry. Just add every now and then.

Am looking at doing the rear seal, but will look at the pcv first.

Thanks for the advice!

 

[OT]

Leave a post and let me know how it turns out. Good luck

 

[mudhound32]

My '89 would always run at 25psi cold and would go to 37psi under most circumstances. Then about 1 month ago it was starting to act funny meaing at idle the pressure would be at 60-65psi and under acceleration it would either stay or drop to 50.
Then yesterday when I started up the needle was to the extreme right way past 80. I freaked and shut it down. I checked the oil sending unit and found the plug was just about off. I cleaned with contact cleaner and applied dieletric grease and is now back to the low pressure I remember and feel comfortable with (over 200k mi). You can try hooking up a manual oil pressure gauge to get a better reading, but if your unsure or if the basic checks don't make a change, you may want to get it checked out.

 

[OT]

good idea mudhound. i'll try that in the morning