Ugh! Overheating!! Maybe...

I've been chasing an overheating problem on the car for a few days... Our last engine would overheat when we had air in the cooling system, and since this engine was just installed (and shares the same cooling system design) that seemed the likely suspect! After purging and purging and checking the thermostat and gauge, it now looks like the temp sending unit on the engine has gone bad! Perhaps it got bumped during removal/installation...