acbanuchi

Okay, yes...this is my first time on f150forum and I will continue to be a member because I just bought a 1991 f150 and I will introduce myself as well as post pictures, but right now my biggest concern is my oil pressure.

Here's the details:

I bought the truck approximately 3 months ago. I had to perform some maintenance on it to make it road worthy, but it's in rather good shape.

Anyway, I changed the oil a couple weeks ago and from the moment I changed the oil my oil pressure has been low. Up until I changed the oil the pressure had always read normal. After trouble shooting the guage and the pressure sensor switch, which both are working properly, I put a guage on it and the motor is only producing 5 pounds at idle and 15 pounds at 2500 rpms. I am not entirely sure what would cause this.

ANY advice is greatly appreciated. Thank you in advance!

mgbk1200rs

drop the oil pan, clean it and the oil pickup screen, check if the assembly is totally gunk free including the pickup tube. If they are in good shape check your oil pump,or replace or fix that, check your oil filter, check for a blockage in the filter bypass system. Also get a Chilton book about your truck, they have trouble shooting info.

13Harleyfan

Always go back to the last place first, what weight oil did you use and how many miles are on that engine. Are you noticing any smoke from the exhaust-engine noise etc....

papa tiger

Are you using 5w30- 10w30- 10w40- 15w40-20w50 ? Are you sure the oil filter? It is possible to purchase a defective filter. Although rare. Don't put 5w20 in it. If you have metal pieces or brass/aluminumgrit in the oil pan bottom you have main/rod bearing problems. The clog at the oil pump strainer is possible, especially if the former didn't change the oil for 30,000 miles. Really bad valve cover internal looking mess is bad now. What did the oil you drained out look like?

acbanuchi

Hmmmm...this is a lot to troubleshoot, but I really appreciate the advice.

I'm using 5w-30 weight oil.
The old oil was definitely burned up.
I was scared the filter was the culprit so I changed it twice with no result.
The truck doesn't smoke one single bit.

I've also asked my friends and they seem to think it could be the main bearings. Right now I'm leaning towards replacing the motor because I would hate to start replacing things just on a hunch.

Can anybody recommend a good place to get a good 302 long block?

papa tiger

Maybe a try at seafoam in the motor oil for a good warm up and drain. Maybe it will clean out some of the nasty stuff and let it circulate. But probably mains and rods are in the bottom of the pan as metal pieces. This is the low oil psi wear cause usually, unless the oil PSI fails abruptly. Sometimes a 15w40 / 20w50 dose in the pan raises the oil psi for a while until furthur wear makes it unusable. Usually at this point the bearing go fast if you goof. I would put 20w50 to er and see if she responds.

acbanuchi

Thank you for your input all who replied. I think I'm going to replace the black and heads. I wouldn't want to replace any major components just to have other old components fail.

papa tiger

It does sound like it ran too long with low oil PSI and smoked the pistons and crankshaft bearings. I'm sure you used the right filter and installed it properly.