My temp gauge is redlining 10 min. into the engine running I'm wondering if there is any coolant actually in the engine/radiator. When I take the cap off the radiator I don't see any coolant. The coolant level is at the cold mark on the overflow tank but how is that really an indicator of the coolant level in the engine/radiator? There isn't a line that runs back to the radiator from the overflow tank so how would they equalized them selves?