Aero V6, Coolant loss without a leak

Probably need to leave vehicle at repair facility until source of coolant loss can be successfully determined .. System pressure testing is a good place to begin diagnosis.. Pressure may need to be left on system for an extended period while vehicle is parked in the shops service bay - - sometimes overnight .. Next morning a puddle of coolant on the floor is an obvious clue. Engine block porosity IS in fact a leak ! Good luck!