Engine cooling system plays an important role to maintain the operating temperature of engine. The coolant circuit initiates by picking up heat at water jackets. With the pressure gradient exists in coolant circuit, hot coolant flows out from engine to radiator or to bypass circuit (during cold start). The under hood air flow carries heat away at radiator after the air flows through numerous hood components. The coolant flow circuit and air flow circuit meet each other and exchange heat at radiator. Extensive researches are carried out to study vehicles' cooling system extensively either numerically or experimentally. The research covers many individual topics which include numerical modelling of engine cooling system, under hood air flow, heat transfer at water jacket, heat transfer at radiator and coolants' after-boiling phenomenon. (C) 2012 Elsevier Ltd. All rights reserved.