Not trying to hijack,

I have the same issue on my 04 Tahoe. 5w-30.

About same pressure as you when it's cold and doesn't like to move until warmed up. But once its warm, I can run that motor very hard and I'll see oil pressure at WOT go high, almost pegged, like it normally did when I first bought it. But in the summer months, or any time above 25 degrees, its at normal pressure.

Keep us updated if you find anything! It's dropped from 50* here to 10* in one night... and this pressure issue scares me with those temps.

 

I talked to engine builder tonight he said he knows it's sludge on pickup screen and to run engine flush for 30 minutes at idle. Dump and do it again.

 

I was also thinking oil filter bypass valve

 

Well I drained the oil. Put 4 quarts of diesel in the engine and let it sit over night. ( did not run engine with diesel) drained it and it was still pretty clean.

Next I put 4 quarts of 10w40 and 2 quarts of gunk motor medic and let it idle 30 minutes with new filter and dumped. Looked like new oil coming out.

Borrowed a scope from a buddy and looked inside engine from drain plug hole and it's extremely clean. Pickup screen had no gunk whatsoever. I put a new oil filter bypass in block I will put straight 5w30 in it with no cleaners and a new filter and see if its. Fixed. It had 30psi cold with the 10w40 and 2 quarts of motor medic.

 

My guess would be it is oil pump or pickup tube o ring related. I know your tired of throwing parts at it but according to the mechanical gauge your oil pressure seems to be within spec. Dont forget that any wear in the main/rod/cam bearings will cause the oil pressure to be a little low. I say just run a good quality oil and filter and keep a ear out for any unusual noises until you really figure out whats wrong with it.

 

Yeah I'm pulling it apart and putting in updated o ring and new timing set

 

I pulled pan and checked pickup tube for leaks and cracks it was fine. O ring was black and crusty and flat on the sides. Put ls2 timing chain in it along with new sprocket s all new gaskets and I fired it up and it has 47lbs cold idle now.


So it's good to go !!!

 

So what your saying is the o-ring on the oil sump tube was the culprit ?

 

Yes it was the o ring, I bought a gm red one, Still was hoping it would fit a little more snug than it did, but oil pressure is almost 50 psi now with amsoil 5w30 and a napa gold filter so i'm happy.

its about 33-34 at hot idle after getting on it. It will go all the way up to 80psi by 4500rpm, Has about 50 cruising hot at 2000rpm

 

How often do you change the oil? I have 215k and when driving I'm at 58
My oil changes are at 3-3300k. Always have been.

But since reading your thread methinks it may be time for a new timing chain, due to some slop sounds coming from the motor.

Glad you found the cure.