ENGINE COOLING APPARATUS AND ENGINE COOLING METHOD

An object of the invention relates to a cooling system for an engine having an EGR system and the like and a cooling method for cooling the engine and is to provide a system and method for cooling an engine which realize a reduction in the capacity of a main radiator by giving a sub-radiator a function to assist the main radiator, a reduction in cost and an effective use of an installation space. A sub-control valve (22) is provided which detects a temperature of a liquid coolant in a main circulation path and separates part of the liquid coolant which is to be sent to a main radiator (16) to send it into a sub-circulation path in case the detected temperature of the liquid coolant exceeds an upper limit value of the temperature of the liquid coolant when an engine runs in a steady state, and the liquid coolant which is sent into the sub-circulation path (12) by the sub-control valve (22) is cooled in a sub-radiator (28) and is then caused to flow into a cooler device, while the liquid coolant in the sub-circulation path (12) is separated to be returned to an upstream side of a first pump (18) in the main circulation path (8).