Join Date: Mar 2012
Location: Mountains of NM
Car: 2012 limited, white, no moonroof or nav
Feedback Score: 0 reviews
One more possibility........You say you had lower radiator hoses replaced......If they are not stiff enough, the hose can collapse under suction from the water pump. This would only happen at high RPM, and would account for the heater not putting out hot air, until the engine is shut down and restarted......(Vacuum would be relieved when the engine shuts down).
If you can easily close the hose with your hand, this could be the issue. I don't know the design of these hoses, but if they are supposed to have a spring inside, and it was left out, that would be your problem. Good luck.