"Homer does that routinely. Thanks for the suggestion though! "

You took it to Home Depot?

A head can overheat even with good coolant temps.

If the liquid level is physically lower than the top of cooling system an air pocket can form in the high spots. ( and stop the heater from blowing hot air ) the head receives sporadic cooling and runs hotter than the rest of the motor. Overall coolant temps are OK because you have good flow through the rad.

Coolant temp is an average of the hottest part of an engine. And, if all coolant is lost, the gauge won't read high as the sensor needs coolant touching the tip to be accurate.