Inspect the bells for signs of glazing or cracking, a glazed belt will be perfectly smooth from slippage, a good bell will have a slight texture of fabric. Cracks will usually start at the inside edge of the belt and spread outward, thus requiring immediate replacement of any worn or damaged drive belts. As a preventive measure in service, it is advisable to replace all the drive belts at the same time. To check the tension of the drive belts depress a flat part of the belt between two components, proper tension is indicated by a movement of 1/4-3/8 of an inch otherwise adjustment or replacement is required if the belt is old and stretched. For V-belts, before making an adjustment, check the V-belt, loosen the adjustment bolts, and turn the accessory to increase the belt tension, and check the tensions when supporting the accessory. If the tension is satisfactory tighten adjusting bolts and recheck. In contrast, serpentine belts use an automatic drive belt tensioner, and therefore don't need any adjustment. For removal and installation of V-belts, disconnect the negative battery cable, loosen the mounting and adjusting bolts, and move the accessory to its loosest position, before removing the old belt. Check Pulleys Check for dirt and install the new belt with gentle pressure in the direction of rotation, adjust the tension, retighten the bolts, and reconnect the battery cable. For serpentine belts, get the negative battery cable disconnected and use a suitable tool to rotate the tensioner and release tension or remove the belt and note how it routs to the location of the new belt, then place the new belt around the accessories and crankshaft and make sure that the belt has the correct rout and has the correct tension then reattach the battery cable.