Hello and welcome to Just Answer!
Do you know if the rad cap was pressure tested or replaced? The rad cap has a pressure rating and if the cap can't hold pressure in the system, the coolant will boil out into the overflow bottle and the engine will overheat.
by lower unit she ment the the distribution manifold and heater hoses as well as the 205 and 170 degree thermostats. this was reccomended by the dealer from a tech bulletin from chrysler. no antifreeze is ever visible. the head gasket was also tested.
no fluid is contaminating the oil as well. just drove for three hours across florida and back with no problems.
I am going to have to opt out and see if any other Expert has run into this!
Sorry I couldn't help you! Good luck!