The alternator drive belt, also known as the fan belt, is an important part of your car's engine. The alternator drive belt charges the alternator when the car is running, as well as powering the water pump and steering mechanisms. When problems arise with the drive belt, you may hear a loud screeching noise from beneath the hood, as well as a loss in power to the car.
The most common cause for screeching beneath the hood is a slipping alternator belt, reports the Automobile Association. This type of screeching is usually heard right after starting the engine, but can also be heard when turning the car slowly or after driving through a deep puddle of water.
While screeching is the most common symptom of a slipping alternator belt, there are other signs that occur with this problem. According to the Automobile Association, some other frequent signs are the dimming of headlights while the screeching noise occurs or a dead battery if the battery goes long enough without being charged by the alternator.
The alternator drive belt can become worn, stretched or incorrectly adjusted over time, especially in diesel vehicles with heavy duty batteries that place a heavier load on the alternators, reports the Automobile Association. The drive belt can also become worn or stretched when the power steering pump is working harder to turn the car slowly, or when the alternator is trying to re-charge the battery when the car is turned on after a long time.
Another problem that can cause screeching from beneath the hood is water pump failure. The water pump is a part of the car's cooling system and can become worn or damaged over time. According to autoeducation.com, the most common signs of water pump failure include screeching, coolant leaks on pavement and strong coolant odors inside the car while driving.
