Many experts urge replacing belts, radiator and heater hoses at specific recommended intervals to prevent your car from breaking down. Losing a belt today means big trouble for the engine because serpentine belts are used on most engines to turn the water pump, alternator, power steering and air-conditioning compressor. If the belt snaps, everything is lost and you may be stranded. Older cars use individual V-belts for these various accessories. A blown hose results in an overheated engine and can cause additional engine damage.
It's not easy to know the true condition of a belt or hose by its outward appearance because most belts and hoses fail from the inside out. Rubber hoses can become hard and brittle, deteriorating with age and exposure to heat, causing the hose to split, blister or leak. Belts also break down with heat, mileage and age. Every time a belt passes around a pulley, it bends. Flexing produces heat that causes the rubber to harden over time. In addition, if the belt is loose or slips, the wear process can be accelerated.
*Courtesy of Car Care Aware