Unlike when a timing belt or chain snaps, the breaking of the serpentine belt isn't nearly as serious. In other words, it won't cause immediate and catastrophic damage to the engine. However, as the serpentine belt is responsible for powering numerous components in your car, having it break will deprive you of these accessories. For example, you'd notice that you no longer have power steering, as the serpentine belt powers the power steering pump. Moreover, your alternator will stop working, as the battery slowly loses charge. In addition, with the water pump no longer working, your hot engine won't be able to be supplied with fresh, circulating coolant. The AC would also stop working since a car's AC compressor derives power from the engine through the serpentine belt.