The drive belt system may use 1 belt or 2 serpentine belts. There also may be a V-belt used to drive certain accessory drive components. The drive belts are made of different types of rubber – chloroprene or EPDM – and have different layers or plies containing either fiber cloth or cords for reinforcement.

A belt or hose failure can cause an overheated engine, loss of power steering, and loss of the electrical charging system. If a hose leaks coolant or the belt turning the water pump snaps, the cooling system is inoperable. If the engine overheats, it can suffer serious internal damage that requires expensive repairs. Overheating can occur anytime, but usually happens in the summer, when the under-hood temperatures are much higher, and heat can trigger or accelerate the deterioration of rubber compounds.

Coolant & heater hoses

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. Designed to hold coolant under high pressure, hoses are also subjected to fluctuating extremes of heat and cold, dirt, oils, and sludge. The most damaging cause of hose failure is electrochemical degradation (ECD), which isn’t easy to detect. According to engineers for the Gates Corporation, a parts maker, ECD attacks hoses from the inside, causing tiny cracks. Acids and contaminants in the coolant can then weaken the yarn material that reinforces the hose. Eventually, pinholes can develop or the weakened hose may rupture from heat, pressure, or constant flexing.

The upper radiator hose fails more often than any other hose, followed by the water pump bypass hose (if your vehicle is so equipped), and the outlet heater hose from the engine to the heater core. Experts recommend, however, that all hoses be replaced at least every four years or when one fails. Always use replacement hoses designed to fight ECD. Gates uses “ECR” for Electro-Chemical Resistant, the Society of Automotive Engineers standard signifying “electrochemical.” Most vehicles built after 1993 come with ECD-resistant hoses.

Accessory belts

Elements that attack attack belts: heat, oil, ozone, and abrasion. Almost all domestic vehicles built today have a single multi-grooved serpentine belt that drives the alternator, water pump, power-steering pump, and air-conditioning compressor. Older vehicles may have separate V-belts that drive the accessories. Chances of a V-belt failure rise dramatically after four years or 36,000 miles, while the critical point for a serpentine belt is 50,000 miles. Many new composite belts don’t show signs of wear until the failure occurs.

Serpentine belts are usually kept tight with an automatic tensioner. Signs of a belt-tension problem include a high-pitched whine or chirping sound and vibration noises. Without proper tension, belts will slip and generate heat or fail to turn the accessories. Always consult your owner’s manual for routine maintenance procedures.