I just bought a 2003 GMC 2500hd with the Duramax and the 6sp manual and 126000 miles. The very next day, I changed the oil, filter, fuel filter, and air filter. Took it down the road and have low oil pressure with the message flashing "oil pressure low". At 1500 rpm or so, the psi is about 30, 7-9 psi at an idle when the truck is warmed up. When the truck is cold it will idle around 60-70 psi. A friend of mine has a Snap-on scanner and we verified that the gauge isn't the problem because his scanner was showing the same pressures. I then replaced the oil sending unit hoping that was it. No help. Now I am thinking oil pump. My theory is the truck has had a hard life and the main bearings and the rod bearings are worn, letting pressure leak by. I figure if the main and rod bearings are replaced my pressure will come back but also put a new pump in to be safe. Any help on this matter would be greatly appreciated! Thanks in advance.

 

No one has any ideas?

 

what brand and weight oil is in it? could also be deluted thin oil from a leaky line or injector under the valve covers. I run delo 15w40 and cold idle I see 75 psi warm idle 45 psi 175,489 miles on her

 

Right now it has mobil 1 delvac 15w-40 in it. I keep checking it for fuel in the oil but I can't detect any.

 

maybe cut the old oil filter open to look for metal? I don't think a engine with that few miles could be hurt but I could be wrong. does it have power issues or funny sounds?

 

It runs great. Plenty of power,no knocks or funny sounds. Just low psi. I am racking my brain here.

 

yeah me to humm

 

any fuel in the oil?

 

I've been checking pretty regularly and I can't smell any on the stick.

 

is the oil level rising?