2008 Jeep Grand Cherokee Owner's Manual - Page 398

398 MAINTAINING YOUR VEHICLE Drive Belts - Check Condition and Tension Belt tension is controlled by means of an automatic tensioner. No belt tension adjustments are required. However, belt and belt tensioner condition should be inspected at the specified intervals, and replaced if required. See your authorized dealer for service. At the mileage indicated in the maintenance schedule, all belts and tensioner should be checked for condition. Improper belt tension can cause belt slippage and failure. Belts should be inspected for evidence of cuts, cracks, glazing, or frayed cords and replaced if there is indication of damage which could result in belt failure. Low generator belt tension can cause battery failure. Also, check belt routing to make sure there is no interference between the belts and other engine components. Spark Plugs Spark plugs must fire properly to assure engine performance and emission control. New spark plugs should be installed at the specified mileage. The entire set should be replaced if there is any malfunction due to a faulty spark plug. Refer to "Fluids, Lubricants, and Genuine Parts" in this section for spark plug information. Spark Plug Wires The spark plug wires should be kept clean and properly connected. Terminals should be fully seated. Cracked, damaged, or faulty wires should be replaced. Engine Air Cleaner Filter Refer to the Maintenance Schedule for recommended Engine Air Cleaner Filter change intervals.