To remove a drive belt from a car engine, locate the tensioner pulley, place the correct size socket and ratchet on the pulley nut, pull the ratchet handle forward to release the belt tension, and lift the drive belt off of the pulley. Most newer model vehicles employ one serpentine belt to drive all of the devices required to operate the vehicle, while many older model and vintage cars employ multiple belts to serve the same purpose.
The drive belt is the long belt on the front of the engine. Identify the tensioner pulley by the spring or pivot point attached to it. Before removing the drive belt, make note of its exact position and the pathway it uses to route around the other pulleys on the devices that it drives. If the drive belt is not replaced in the same location, it does not work. Many vehicles have a belt diagram located underneath the hood or in the owner's manual that shows the correct routing pattern for the serpentine belt.
Measure the serpentine belt carefully to ensure you get the correct replacement size. The drive belt system on most newer cars comes with an automatic tensioner that tightens the belt for you.