A cooling system for a turbo-charged internal combustion engine utilizing a unified flow control valve capable of changing the mode of operation of the system in response to a varying heat demand. The unified flow control valve may be a solenoid operated slider valve having a cylinder with connections to the engine water jacket outlet, the intercooler inlet, the radiator inlet and outlet, and the water tank, and a piston having rows of openings which when aligned with the cylinder connections provide flow paths corresponding to various modes of operation.