ENGINE COOLING SYSTEM

This engine cooling system suppresses increases in vehicle weight caused by employing a Rankine cycle, makes it possible to improve the performance of the Rankine cycle, and is provided with: a Rankine cycle (31) configured such that a coolant (30) circulates a cooling pump (25), an evaporator (26), an expander (28), and a condenser (29) in this order; an engine main body (10) in which a turbocharger (6) is arranged in an intake passage (5) ; a radiator (3) through which cooling water (18) for the engine main body circulates. The engine cooling system is configured so that: a sub-radiator (2) is installed parallel to the radiator (3); compressed air (8) that is compressed by the turbocharger (6) is used as a heating source for the evaporator (26) ; and the outlet-side cooling water (32) of the sub-radiator (2) is used as a cooling source for the condenser (29).