Patent ID: 7124715

Claim:
An engine cooling system comprising: a primary cooling circuit having: a pump for pumping liquid coolant to an engine; an engine return line for coolant returned from the engine; a radiator having a inlet side and an outlet side; a bypass; and a primary flow control valve and a pump return line, the primary flow control valve and the bypass being connected in parallel with the radiator inlet side and the bypass connected to the engine return line, the radiator outlet side and the bypass connected to the primary flow control valve and the primary control valve being operative to control flow as between the radiator and the bypass to allow fluid to flow from the radiator only when the sensed temperature of the coolant is above a normal running temperature of the engine; a secondary cooling circuit having a heat exchanger and a temperature responsive control valve, the heat exchanger being connected to the pump return line and to the temperature responsive control valve and the temperature responsive control valve having a first inlet connected to the engine return line upstream from the radiator, a second inlet connected to the outlet side of the radiator and an outlet which is connected to the heat exchanger; and a heater circuit comprising a passenger compartment heater connected to receive coolant heated by the engine and return it to the pump return line; the temperature responsive control valve being operable, depending upon the sensed temperature of the coolant, to shut off flow through both of the inlets simultaneously, to shut off flow through the first inlet while permitting flow through the second inlet and to shut off flow through the second inlet while permitting flow through the first inlet.