I have a GMC 7000 with the 8.2 Fuel Pincher in it. It has been a good truck and engine for us. I drove it for the first time in a while (hired man usually drives) and noticed that the oil pressure was running low after it was up to operating temp.

Oil pressure is 50 psi at start up and fell to 30 when running hard at operating temp. When I pulled over at idle the pressure was 18 psi! After it sat for 15 min. it was 40 psi but when I got back on the road it went down to 30 again when coolant temp went back up to normal op temp. I am sure that it never used to run this low. I checked everything, oil level, coolant etc., all appears to be normal. I double checked oil pressure with a second gauge temporarily plumbed in.

What is most likely to be going here?

I thought that first I would rebuild the oil pump and check the relief valve (they are mounted on the front of the engine).

If that does not do it I thought that I would drop the pan and spin in new bearings.

What do you think?

Thanks for your time,
JP.

 

Oil pump would be the easiest to do first. If that doesn't do it, time to rebuild the bottom end.

 

Are you sure that the truck is using the same weight oil as before? That will make a difference. Otherwise, it sounds like you need to start accessing the pump and then moving from there.

 

Geeeeezzzz people how about checking the psi guage first. The fuel pincher was not that great of a motor to start with, but the oil pump was not usually the problem. Bearings are always the first things to go.

 

sounds low, but I check in the morning..
i have the same engine in my bus.
is yours a turbo? wnad what HP? there are several versions of the 8.2
coolant temp vary from 160 to just over 190..after to warms up the winter to 100+ degrees days in the summer. is it an auto? mine is and the tranny temp will rise at a stop in hot weather..I've 250F at idea. normally is 170F or less. I just popped into neutral and the temps dropped.

-dkenny

 

For the record the problem appears to be bearings.

I checked regulating and relief valves and they were clean as a whistle. Since the oil pump is a bear to get at, even though I already have the hood and rad out, I decided to check bearings next. The pan is real easy to get off of this thing and I've been wanting to put a new pan gasket in anyways.

I took off #4 first because it has the thrust bearings on it. The lower main is worn right through to the copper. So... I will turn in new main and rod bearings and see what happens.

The engine is 165 HP NA with a 5 speed. The truck is a dog but works good for our needs.

Thanks for the help,
JP.

 

That's the way to spec 'em for paid drivers - not enough power to hurt the driveline.

 

Wanna;

I didn't want to say it but... bingo.

The truck has a tall 22 foot box on it and will just about do 60 mph. In a headwind 50. With 6 tons on it gets 8 mpg, empty over 10.

It has treated us well and we love it.

JP.

 

My oil pressure runs around 70 at speed and 25 at idle.

I think mines a 190HP turbo with a 4 speed MT643..runs nice and drives well. gets about 7mpg on the road. but the bus weighs around 22k

-dkenny