Hoses are the cooling system's weakest structural component. They are made of flexible rubber compounds to absorb vibrations between the engine and radiator, or, in the case of heater hoses, the engine and body's firewall.

The hoses in your vehicle connect to the radiator, heater, fuel lines, vacuum lines, air conditioning, and power steering. Portions of hoses connected to the engine are flexible to absorb vibrations from the vehicle. Most often hoses will wear from the inside, appearing stable on the outside.

Hoses should typically be replaced every four years. Because of the cost and extent of the damage that can be caused from a broken belt or burst hose, it is good to have a mechanic regularly check these things and to err on the side of caution.