SHOP TALK Damaged fan shrouds can usually be repaired if the damage is not severe. Polyethylene and polypropylene plastics can be hot-air or airless welded. Fiberlene can be glued with epoxy. The important rule Here is never leave a fan shroud off. The shroud is needed to help the fan work at peak efficiency and leaving it off will affect the fan's efficiency.Checking Belts If a belt breaks, at best the fan stops spinning and the coolant does not cool down efficiently. At worst, the water pump stops, the coolant does not circulate, and, eventually, the engine overheats.Belts, like hoses, are made of elastic rubber compounds. Although they are extremely sturdy, they are primarily designed for transmitting power. Even the best belts last only an average of four years. Advise the customer to replace all belts every four years, regardless of how they look.Fortunately, belt problems are easily discovered either by visual inspection for cracks, splits, glazing, or oil soak- age, or by the screech of slippage A glazed, cracked, or damaged belt should always be replaced. In servicing a multibelt setup, it is very important to replace all of the belts when one belt is bad.Also inspect the grooves of the drive pulleys for rust, oil, wear, and other damage. If a pulley is damaged, it should be replaced. In many cases, rust, dirt, and oil can be cleaned off the pulley and should be removed before installing a new belt. Also check the alignment of the pulleys.Misalignment of the V-pulleys reduces the belt's service life and brings about rapid V-pulley wear, which causes thrown belts and screech. Undesirable side or end thrust loads can also be imposed on pulley or pump shaft bearings. Check alignment with a straightedge. Pulleys should be in alignment within 1/16 inch (1.59 mm) per foot of the distance across the face of the pulleys. Belt Replacement V-belt replacement is a straightforward procedure but care must be taken to install the new et correctly and under the correct amount of tension.Before removing the old drive belt, disconnect the electric cooling fan at the radiator, if the vehicle has one. Re- hove the old drive belt by loosening the components that have adjusting slots for belt tension. Then slip the old belt off.Always use the exact size of replacement belt. The size new belt is typically given, along with the part num- on the belt container (Figure 12–64). You can ver- what the new belt is a replacement for the old byphysically comparing the two. This comparison, however, does not allow for any belt stretch that may have occurred. Therefore, use this comparison only as verification. The best way to select the correct replacement belt is through the catalog and/or by matching the numbers on the old belt to the numbers on the new belt.Place the new belt around the pulleys. Once in place, tighten the component mounting bolts that were loosened during belt removal. Then adjust the tension of the belt and retighten all mounting hardware.When installing a serpentine belt, make sure it is fed in and around the accessories properly. Service manuals show the proper belt routing. Also make sure the belt tensioner or idler pulley is working properly. This pulley may be a spring-loaded tensioner (Figure 12–65) or an adjustable pulley. If the adjustable tensioner pulley is not spring loaded, adjustments are made with a jackscrew or with an off-center pulley bolt. To loosen the tension of the belt, turn the bolt in a counterclockwise direction.Before removing a serpentine belt, locate a beltouting diagram in a service manual or on an underhood decal. Compare the diagram with the routing of the old belt. If the actual routing is different from the diagram, draw the existing routing on a piece of paper. To install the new belt, wrap it according to instructions. Make sure the ribs of the belt are seated in the matched grooves on the pulleys. Once the belt is fully routed, put tension on the belt and adjust it to specifications. Belt Tension Correct belt tension is essential for long belt life and quiet operation. Loose belts may slip on the pulleys and not drive the components at their proper speed. This situation can cause numerous problems, such as low generator output and noise. Excessive tension can also result in noise as the driven components rotate under stress. This stress can lead to premature bearing and bushing failure in water pumps, generators, and power steering pumps.