Engine warning light comes on and oil pressure gauge bottoms out only when the motor is hot and been running a while. As soon as I'm on the gas it goes right back up to operating range. I've put a manual gauge to the oil pressure sending unit 'which is new' and it measures approx 6lbs avg. triggering the light which responses to pressure lower than 8lbs. This I know as fact so far, but does this motor have any hope? The previous owner over heated it real bad and I fear for the main bearings. Is there any way to know for sure or could it be oil pump related? Any thoughts..

 

I was 4 wheeling this weekend with a fully loaded cherokee and at idle the oil pressure went really low and triggered the light. If I gave it gas, the oil presssure went up and the light went out. The engine got hot but did not overheat. I am running 10w-30.

I am interested in answers to your question.

Flash

 

Check the oil pressure sending unit, there not expensive and install easy.

 

How much leakage have you observed? There's an o-ring kit for the oil filter adapter available at the stealership for short money (believe it or not).

 

My oil pressure is and always has been low at idle when it is hot. I keep telling myself that I'll put in a high pressure pump in when I get a rebuild. 260,000 miles and I am still making the same threat. I talked to a mechanic at the dealer when I first purchased it in 98 and he said it is normal. It always hovers at just a hair above the first line, until I apply pressure to the gas pedal that is. I can’t say that it ever went low enough to bring on the light. From my experience, overheating a motor has caused problems with head gaskets and or head, blown hose, water pump failure etcetera. Running one out of oil could probably mess up anything that moves in a motor.
Sorry! I know this didn’t help but if I had to guess, you would probably have to pull the pan and take a look.

 

If you put a mechanical gauge on and it shows low pressure, its either the pump or bearings. Spec is for 13+ psi at 600rpm and 37-75psi when running.

 

Mine has always done this same thing. I talkled to many many people about it but always got the "if your motor runs like it should, it's probably the sending unit" so im guessing thats all it is. Havent gotten around to it yet. I have some leaks but im gonna get a filter o ring and im planning on changing my valve cover gasket as well.