COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINE

To construct a cooling system at a reduced cost which may restrain overheat of an internal combustion engine even in a case where a valve for controlling a cooling medium is broken down. A first flow passage supplying the cooling medium of the internal combustion engine to a radiator and a second flow passage branching from the first flow passage by a flow control valve to supply the cooling medium to a first heat exchanging portion are provided. In addition, a third flow passage provided separately from the first flow passage to supply the cooling medium to a second heat exchanging portion via an on-off valve is provided. A control apparatus controlling the on-off valve and the flow control valve based on a temperature of the cooling medium is provided.