Smokerbill
Crossing the Road
It could be a small leak in the radiator core too. I had that happen with a Camry I used to own. The overflow was full, but it overheated. The radiator was almost empty. Had to get a new radiator to fix the problem.If you keep the reservoir full, it should keep the radiator full. If it's not, then you have another small problem with the overflow hoses or the radiator cap.