Accessory drive belts and coolant hose replacements are perhaps the most popular and lucrative add-on services in the independent import shop. Because belt and hose inspections are included in auto manufacturers' scheduled maintenance charts, service writers at most well-managed shops recommend a belt and hose inspection along with tuneup, oil change, starting, charging, cooling, air conditioning and power steering system services. The potential exists with each belt and hose inspection to add an average of $100 or more in needed replacements to any service, whether it be a routine oil change or a complete engine replacement.

Most belts fail from a normal aging process, which means that the rubber in the belt eventually develops cracks that result in a broken belt. Some belts, such as the alternator belt and power steering belt, wear faster because they transmit high torque under specific driving conditions. The demands of increased torque subsequently cause higher operating temperatures that accelerate oxidation and wear. Other belts, such as an air injection pump or water pump belt, transmit very little torque and are, therefore, subject to very little wear.

Oil contamination is perhaps the major contributor to early belt failure because oil tends to deteriorate and lubricate the belt material, which, in turn, causes the belt to slip. Consequently, oil seal replacements often go hand-in-hand with belt replacemen...