Percolation? Heat soak? Don't drive during summer??

dartfreak75 said

Yes! The cooling system should keep the engine at a safe temperature regardless of the outside temperature or it something isn't working right.

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Nope. An air cooled radiator can only achieve to much drop in temperature, the higher the air moving across it, the less heat it can remove from the coolant. An enclosed garage situation is unique and not a performance threshold of any kind.