okay... 2001 Yukon with the 5.3L. bought the truck with blown head gaskets (it also has a whipple supercharger on it) and it did have water in the oil... got the head gaskets done (and heads machined) and everything back together and fired it up... let it sit there and run for a minute or two and i noticed the "check gauge" light was on and the oil pressure gauge at 0 and the temp gauge started creeping up. shut it off, checked oil looked good and clean... started it back up and it had oil pressure for about 10 seconds then went back to 0. do you think the oil screen could be clogged? it was not making noise or knocking/ticking... thought about running some motor flush through and see if maybe the screen is clogged? what should i do?

 

The oil pressure sensor is probably crapped out from the water. I'd recommend a new one first, then see if you still have pressure fall off. 0 pressure is an immediate STOP warning- just a few seconds without pressure will do irreversible damage to the bearings.

 

I can corfirm that even a few seconds of no oil pressure is no bueno lol

 

If you had water in the oil especially on a supercharged engine it's probably done for especially since you don't know how long and you bought it like that.

Water can not be compressed and when it goes through the oiling system its like glass. It will tear up the bearings and wreak havoc on things like sensors.

Now depending on how long the oil/water sat in the engine you might get lucky and find the muck at the bottom clogged the OIL pick up. Though chances are the guy kept running it until there was no oil pressure and parked it thinking oh it just needs head gaskets that's why there is no oil pressure... People are often miss-informed regarding the oil system. See the pictures of the oiling and what the basics of a gerotor pump look like.

I have a feeling the Oil pump is ruined. While the gears are steel the housing is just aluminum and since you can't compress water it probably tore up the inside of the housing.

When you drained the oil/water did you see any metal particals??? It would look like a fine silver powder in there almost like anti seize mixed in. What about the new filter??? Did you pre-fill it with oil???