Turn the Heat on high max, are you getting any heat?
Poor circulation of coolant, shortage of coolant, and any air pockets could cause an over heated condition.
1) Use a Prestone flush kit and a garden hose with a little water pressure to force out any air.
2) A plugged Catalytic converter can also cause an Auto to over Heat.
Any local muffler shop can do a back pressure test on your cats.