Coolant loss

[Chamberpains]

I'll bet a large piece that when cummins replaced the head they didn't pull the liner and cut counter bores to shim all the liners to .014 all around (basically overhaul the engine)

Instead they ripped the head off. Checked to see if the liners were within cummins spec (.010) and slapped a head back on. This leaves the liners to low, if not out of whack with numbers all over the place around all the liners. Then through normal use, the piston grabs the weakly positioned liner and makes it dance up and down every stroke (dropped liner) or something along those lines.

Drop the pan like tree98 said. Also eliminate the air compressor as a cause to coolant in the oil. But track records show chances are slim its not a dropped liner.