Nuke have you tried changing the thermostat since all this started, or just remove the thermostat and try a test run. Without the thermostat the car may stay in the closed-loop mode but if it does not over heat it is probably a bad thermostat. If it runs hot with the thermostat removed you may have a clogged water jacket in the engine, an air-pocket in the engine, or a bad water-pump. It certianally sounds as if water flow is restricted.

2009 Sorento LX, 4x4, V6, Auto, Red