Originally Posted by RPerry435
there is no coolant flow through anything when the thermostat is closed.
when the thermostat is closed the temp you see is block temp, anything over boiling causes cracked heads/blocks and warped engine parts.
Think about it RPerry, if that were the case you'd only have interior heat when the block got too hot (Fine for Florida, not so good up here in the frigid north
) The heater core is fed from the bottom center of the intake manifold at the front of the engine and returns to the block next to the water pump. The thermostat is on the other end and controls flow to the radiator hose only.