The radiator hose is a rubber hose that transfers coolant from an engine’s water pump to its radiator.There are two radiator hoses on every engine: an inlet hose, which takes the hot engine coolant from the engine and transports it to the radiator, and another is the outlet hose, which transports the engine coolant from the radiator to the engine.Together, the hoses circulate coolant between the engine, the radiator and the water pump. They’re essential for maintaining the optimal operating temperature of a vehicle’s engine.