Originally posted by TheContourGuy:
The Duratec has a thermostat. Without one, the ECU would have no idea what temp your engine is running at, hence it couldn't supply the correct amount of coolant.
the thermostat controlls the amount of coolant that flows through your motor, basically it opens when your motor is hot, closes after it cools, to help the motor warm up faster. this is why you have no heat in the winter for a few minutes.
the ecu gets its reading from the engine coolant temp sensor. (like 2redtours mentioned) but doesnt use this to control the coolant flow. instead, the ecu reads the coolant temp and advances or retards the timing, or leans or richens the fuel ratio, for (somewhat) optimum power and knock prevention.
chitown- be sure to watch the coolant level after all the work is done, if your car looses coolant, the overheating could've caused the head gasket to blow. this just happend to a friend of mine.
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