Low oil pressure

[TimSA]

Hi guys,

Been having low oil pressure for a couple weeks now. It's about 40psi (half way) when just starting and the engine is still cool. Not long after its heated up it drops and when idling down below 10 (1/4) and finally will drop right down and the check guages light comes on.

- I did a manual oil pressure test with an external mechanical oil pressure test kit. Also so far I have:
-cleaned all connectors
- oil change and switched to a thicker oil
- new oil pump
- new sump gasket
- pump gasket and arm
- new oil filter
- another oil change

But still the problem persists. Hardly driving it longer than 5 mins before pressure starts to drop, haven't let the check guages light come on again.

Don't really know what to do next? Any help or ideas welcome.
Also any advise on somewhere to do an engine rebuild if needed

 

[Jerry Bransford]

What do you mean the oil pressure will "drop right down". To what? 0 psi? 8 psi is perfectly normal and acceptable at idle rpms.

 

[TrueTexas]

The gauge on earlier TJs is a real gauge, not a dummy gauge. Download the factory manual from the resources section which will tell you the acceptable oil pressure on a warmed up engine at idle.

What happens when you raise the RPMs? Does the oil pressure jump up to 40+?

 

[Lou]

Per the picture of his manual gauge he has .5 PSI of oil pressure. Im going to guess main bearings are wore out.

 

[TrueTexas]

@Lou I believe the red is psi. Looks like right around 8 psi.

 

[TrueTexas]

@TimSA my dash gauge read about 10 psi lower than actual oil pressure.

Once I replaced it, it started reading much more accurately.

Have you replaced the oil pressure sender?

 

[Lou]

@Lou I believe the red is psi. Looks like right around 8 psi.

Thats my bad!

 

[Lou]

So is the dash reading consistent with the gauge at all times?

 

[TimSA]

What do you mean the oil pressure will "drop right down". To what? 0 psi? 8 psi is perfectly normal and acceptable at idle rpms.

Yep it will drop right down to 0 and check guages light will come on. If you rev a little or drive, as I had to it goes up a bit and light goes off but as soon as you stop or idle it will come back on.

 

[TimSA]

@TimSA my dash gauge read about 10 psi lower than actual oil pressure.

Once I replaced it, it started reading much more accurately.

Have you replaced the oil pressure sender?

I ordered one but it was the wrong size so I bought an external pressure reader. The unit is working as it has picked up the slight improvement with first thicker new oil, then an improvement with new pump and filter but eventually after it warms up it still drops right down.

 

[TimSA]

Per the picture of his manual gauge he has .5 PSI of oil pressure. Im going to guess main bearings are wore out.

Thanks Lou, what I was dreading. It's driving fine and there is no noticeable noise, what other symptoms would point towards this?

 

[TimSA]

So is the dash reading consistent with the gauge at all times?

View attachment 195658

Yep the dash reading is consistent with the manual guage. I wasn't alarmed by 8psi more that it has noticeably dropped recently from what it used to sit at and it has a few times dropped eight down to 0 and check guages light comes on which is not perfectly acceptable :/

 

[TimSA]

What do you mean the oil pressure will "drop right down". To what? 0 psi? 8 psi is perfectly normal and acceptable at idle rpms.

Thanks Jerry, ya drop to 0 as per 2nd pic. That's taken engine on idling.

 

[TimSA]

Thanks Jerry, ya drop to 0 as per 2nd pic. That's taken engine on idling.

 

[TimSA]

Also the oil actually looked pretty good /clean when we changed the sump gasket and oil pump

 

[williambmac]

Have you verified the oil pressure sensor passage in the block is not blocked by sludge? When your pressure is dropping down to near 0psi does the engine begin making any noise? Have you pulled down any main bearing caps to inspect for excessive wear. A worn main brg will allow oil pressure to bleed down.
Does the vehicle use coolant at all?

 

[SkylinesSuck]

Thanks Jerry, ya drop to 0 as per 2nd pic. That's taken engine on idling.

Yeah, that isn't correct. 8psi at hot idle is low. 0 is obviously bad lol. If you have already replaced the sender, oil pump, and verified the pressure with a mechanical gauge, it sounds like there is a good chance you have some excessive bearing clearance i.e. yo shit's worn out. If it were me, I'd band-aid it by running heavier weight oil and/or a high volume oil pump, then start saving my pennies for a motor rebuild and/or upgrade.

 

[Lou]

Just to be sure, when your dash drops to 0 psi does the manual gauge also drop to 0?

 

[TimSA]

Have you verified the oil pressure sensor passage in the block is not blocked by sludge? When your pressure is dropping down to near 0psi does the engine begin making any noise? Have you pulled down any main bearing caps to inspect for excessive wear. A worn main brg will allow oil pressure to bleed down.
Does the vehicle use coolant at all?

Good call checking the passage might be blocked. Checked everywhere else and there was little to no sludge, even on the sieve in the oil pump. Doesn't use much coolant, replaced the radiator about 1000miles ago..

 

[TimSA]

Yeah, that isn't correct. 8psi at hot idle is low. 0 is obviously bad lol. If you have already replaced the sender, oil pump, and verified the pressure with a mechanical gauge, it sounds like there is a good chance you have some excessive bearing clearance i.e. yo shit's worn out. If it were me, I'd band-aid it by running heavier weight oil and/or a high volume oil pump, then start saving my pennies for a motor rebuild and/or upgrade.

Lol yo shits worn out . Not what I wanna hear but you might be right! Not a lot of jeep experts over here for an engine rebuild, and getting parts is a headache