Belts and Hoses
Coolant hoses include the upper radiator hose, lower radiator hose, heater hoses and bypass hose (some engines). Coolant hoses are made of reinforced synthetic rubber made to withstand heat, vibration, pressure, and cooling system chemicals.
Coolant hoses provide a flexible connection for coolant flow between the engine and the radiator and the engine and the heater core.
The coolant hoses should be inspected at least twice a year, both in the spring and in the fall. Hose clamp connections should also be checked to ensure that they're secure and free from leaks. Although hose condition has historically been determined from the outside of the hose, research shows that hoses really begin to break down from the inside out. This process, called electrochemical degradation (ECD), generates fine cracks in the wall of the hose tube. These fine cracks extend from inside the hose tube to the outside, close to one or both ends of the hose. Coolant can then seep through these cracks and attack the hose reinforcement. Eventually the condition worsens to a pinhole leak or a burst hose.
Coolant hoses should be replaced at least every four years, or more often as needed. It's also a good idea to change any hoses that connect to a part of the cooling system that's being replaced. For instance, it's wise to replace both of the heater hoses when replacing the heater core.
If you decide to service your cooling system yourself, use extreme caution: Opening a hot radiator or coolant reservoir/overflow tank can cause severe burns. Be sure that both the engine and cooling system are cool before you begin any heating/cooling system maintenance or repairs. It's possible that your car may be equipped with an air bleed for the cooling system. Unless the cooling system is bled properly, air may stay trapped in the system and cause erratic temperatures, or in extreme cases, engine or cooling system damage. If you're unsure about any aspect of cooling system service, don't take a chance. Have your car looked at by a professional service technician.