Oil leak possible causes.

You might just have to thoroughly power wash the engine and then just run it at 1000 rpm or so and watch for oil drops on the ground. It make take over an hour for anything to form.

 

You have to wash it off as clean as you can, I use Gunk citrus spray, not the foam, that is NVG. then preasure wash, When it is clean, run it at 1500 RPM cover the radiator 90% with a tarp or bag to get it hot, and crawl under and look. Cats have the ability to leak from a lot of places, if it is at the front, the fan will move it around.
Just a thought!

 

Maybe look under the oil cooler.

 

Could it be blowing it out the vent hose?

Give it a good soak with simple green, and power wash it with hot water, just don't get wild around electrical connections with the power washer. Them things aren't meant to keep water out under pressure, in time you will get corrosion in connectors and really be pissed trying to track down electrical problems.

 

Check the radiator for oil. I had an oil cooler go out years ago, and it pushed oil out the radiator and all over the truck. The oil is under more pressure than the coolant, so if the cooler goes, it's a heck of a mess.

 

Check the bungs that go in the spare oil level tube spots in the block, also rocker cover base if it is higher. Possibly sump gasket, take the others advice and clean it good and run it. You should be able to pin point it from there.

 

You need to steam clean it use some good degreaser industrial strength let the engine get hot the steam clean it look for leaks but best to run it around local for a bit and run the crap out of it build some boast it will show up also get some dye and run it in the oil i use cummins brand then get your black light out and trace it back.head gasket could be bad might run fine an blew around the oil drains in the block if it is head gasket make sure to have them check the protrusion I would personally be done with it and counter bore the block it's inevitable