I just bought a 2005 4.8 Sierra xtra cab, after driving a Ford Ranger(Mazda B4000) for 20 years. One thing I noticed when I test drove it was the oil pressure guage was stuck at 80lbs. I did not think anything of it except I figured the pressure sensor would most likely be the culprit. Otherwise I thought it drove great. Today I bought a Standard Ignition brand sensor from Oreillys that had good reviews. Once I got it home I noticed it did NOT come with a crusher washer but a washer with a rubber inner that pushed over the threads. I double checked with the picture on Oreillys and it did show a crush washer. I was like oh well I will put it on It should work -the old sensor was leaking. Once installed, I turned on the car and the oil pressure went to 0. I drove it up the street and the highest it went was 20 psi. About an hour later I drove just over 1 mile and the low pressure warning popped up. I am a bit nervous here. Like I said it ran fine and runs fine even now(drove about 20 miles earlier before the switch out)- no smoke, noises etc. There is some oil on the bottom of the engine.
The car has 135, 000 miles and seems to have been well taken care of, but who knows. It had no previous records. Could it be that it is not really crushed on the car and that is what is helping to cause the low oil pressure? I read of certain oil filters that can cause low oil pressure. This is an Omnicraft (ford brand?)oil filter. Any help, advice would be great.
Mark