I realize I am about 1 year late but I would like to add clarity for those who follow. I had the same issue, no oil pressure when oil was cold but outstanding pressure once motor warmed up. This was my work vehicle(still is) so I had a lot of hard thinking to do. My vehicle has 223,000 on it. Buy or not to buy? (new, that is) My6.0L Vortec was running strong despite the oil issue. I took it to my local Goodyear who changed my oil and filter and installed a new oil sensor. Same problem. Considering the scope of work involved in replacing the pump I opt'ed to get a quote. I've done this work since before I could legally drive but today I run a heating and cooling business and don't have the time to do this. 1. Got quote. To replace oil pump $1000. I am beginning to think spend the money on a new van. 2. I thought, crap, I will have to do this job to justify keeping it. So, I thought I would do the water pump
, timing chain and gears and oil pump. 3. Then, I caught my breath, thought it through and came to the realization that 1. My problem "HAD" to be the O-RING in between the pick up tube and the pump. Did I really need to replace everything else? In my case? No. My motor , no matter how well it is running, probably wont be real dependable after 300,000. Will the timing chain break in the next 75, 000? I googled it and couldn't find anything on them breaking. So, I did not have transfer cases or anything in my way, I dropped the pan and replaced the o-ring. I will not bore you with clean up and torque proceedures. The o-ring left residue inside the pump socket and on the tube it slides onto. I used the only solvent I had available which was acetone to clean it off. I coated some food grade lubricant on the o-ring before inserting the pick up tube. Took my time cleaning up the pan etc. You will need the o- ring, new pan gasket and the external cooler lines gasket. It worked. On single digit mornings I now have awesome oil pressure. The job wasn't bad at all. The new stee/neoprene gaskets are a synch. I am going to post some picks if it works. New and old gasket. The old gasket was once green. The green was what I washed off the oil pump and pick up tube w/acetone. My motor started having this problem around 220,000. It was sucking air around the o-ring when the oil was at its thickest. once it warmed and thinned, the pump would draw it up instead of pull air around the o-ring. I hope this has helped and I appreciate everyone else's help that steered me in the right direction.
- Airstar (Craig)