Cat C12 has mechanics puzzled ..

Need some help here ..
Cat C12 (2KS)
Red Shut Down Light - Low Oil Pressure
Decent amount of Blow By and water dripping from blow by tube.
Drained oil pan.
Pressure up on coolant system. 18lbs for an hour and a half. No change. No Leaks.
Pulled valve cover and there’s traces of water, not coolant, water like condensation. Evidence of rusting on Jake’s.

1 mechanic says to change water pump.
1 mechanic is still looking in to it because he doesn’t think it’s water pump.

Advice and ideas??

 

Run the truck everyday. It was running great, no problems. Pre-Tripped it. On my way to get fuel the Red Shut Down Light came on. Let off the throttle and when the rpm’s came down the red light went off and I got throttle back but lost it again when rpm’s came up and Red light came back.
Hooked up my scanner and it doesn’t read any faults until Red Light comes on and it says Low Oil Pressure.

 

Thank you. I’ll pass along the info.

 

The oil is not milky. There was no coolant in the pan out on the dipstick. But there was a small trace of milky on the cap of the oil fill tube like condensation/steam buildup.