Diesel Bombers - 99 7.3L Oil Pressure Problem.

Hey let me first start off as, this is A 1999 Ford F350 7.3Liter Diesel Truck.

275,000Miles I am the second Owner, The original Owner bought this truck Brand new. I have all of his service Records.
He kept this truck clean and serviced it every 3,000miles.

I know he hauled and used this truck as it was meant to be used. things done on the truck have been.- 1inch Blocks. 35inch All terrain Tires. Banks Power Stinger Plus System. Custom Automatic Transmission with Suncoast Converter, TransGo Tugger Kit, Alto Clutch Packs, Mag-Hytech Pan. 456 gear Ratio.

The High Pressure Oil Pump was replaced at 175,000miles
all Ford Recalled items have been replaced.
other then that nothing else has been done.

Owned it for a while then the Problem started.

Fact 1. At idle the Dash gauge would sometimes flicker and the lite would come on. this would (return to normal) when the RPM was at or higher then 1,000RPM.

Fact 2. my Dad and I put a mechanical gauge on it. Oil Pressure at idle read Zero. at 2,000RPM it still read Zero.

Fact 3. We Diagnosed that, it could be the Oil pressure regulator valve. or the Engine Oil Pump.

Fact 4. Replaced the regulator valve unit. and Replaced the Engine Oil Pump with a Melling engine oil pump.

Fact 5. Put the Mechanical gauge back on. At cold idle read 50psi then slowly came down to 25psi at 2,000RPM read 50psi and held.

Fact 6. (took her up the hill. came back) At Hot idle read Zero. at 2,000RPM read just 25psi.

where's the Oil Going?!? although Replacing the Oil Pump and regulator valve unit made a big difference it's still not where it should be. The Engine is not Knocking it sounds great. so my Dad and I don't think its the main Bearings.

what else could it be? anywhere else the oil could be squeezing by? what I'm I missing here?