The serpentine belt, or fan belt, as some call it, transfers power from the engine crankshaft to the various engine accessories, such as the alternator, power steering pump etc. When the belt doesn’t maintain constant adhesion to the various pulleys, it begins to slip and squeal. Often, the belt squeal is caused by moisture on the ribbed side of the belt.
Checking Things Out
Start the engine and raise the hood. Remember to keep your hands and clothes away from the engine and components. Use the flashlight to carefully look for a place where you can spray the belt with WD-40 in such a way that the ribbed side of the belt is covered just before it travels under a pulley. Oftentimes, the exact place where the squeal occurs can be determined by listening to the sound and watching for a correlation between the sound and belt travel.