Kawasaki FD731V-CS00 Mysterious Coolant Loss

[rpdalton]

This engine was brought to me rough running with substantial low coolant level and the crankcase was coolant contaminated. I pulled both heads, checked for flatness and both were in spec and replaced the head gaskets.
It came back to me with a continuing coolant loss issue. There is no oil contamination now and there was no coolant system loss or coolant in the combustion chambers when pressure testing overnight. The system holds 21 PSI just fine and it looks like it only loses coolant when hot. I pulled both plugs and bore scoped the engine, one piston looks like it was steam cleaned a bit (see photo). Replaced the one head gasket again (with an high temp exhaust RTV sealant in addition) and the engine still loses coolant. Has anyone experienced this? Cracked head or cracked block?

 

[ILENGINE]

Possible gasket leak at the intake crossover pipe leaking into the cylinder

 

[rpdalton]

I replaced the crossover gaskets as well previously. Maybe I should use a sealant on them...

 

[K&K]

Did you ever find a solution? I'm having the same issue. Removed the heads, had them checked for cracks and decked along with a valve grind and valve guide seals. Torqued the heads in the recommended sequence and installed new intake gaskets. The first time I used high temp silicone in addition to the gaskets, second time just the gaskets with the same result. Crack in the block? This engine has 1200 hours on it and never overheated.