The Mazda 3 is the entry-level car in Mazda’s line. Available as of 2010 in a four-door coupe or five-door hatchback, the 3 also offered different drivetrain options for potential owners as well. No matter which Mazda 3 you buy, it comes with a serpentine drive-belt system. This system replaced the old fan-belt system, replacing several belts with one long belt that winds its way through the engine accessories like a serpent--hence the name. You can replace the belt in less than 30 minutes if you have some basic mechanical aptitude and the right tools.
Open the Mazda 3’s bonnet and support it with the prop rod. Look for the serpentine-belt routing diagram printed on a sticker applied to the fan shroud.
Connect the belt-tensioner tool into serpentine belt tensioner and move the tensioner pulley away from the belt with the tool. Hold it steady as you move the belt off the pulley with your free hand. Slowly move the tensioner back into place and then take the tool out of the tensioner.
Pull the belt off the engine accessory pulleys by hand. You may need to access the lowest pulleys through the right-front wheel well or from underneath the Mazda.
Stretch one end of the old and new belts from the ground upward with your hand. The old belt can be up to three-quarters inch longer than the new one due to stretching. If it’s longer than that, or shorter, the belt will not work. In that case, take both belts to the place of purchase to match up the old belt with a proper new one.
Run the new belt around the bottom of crankshaft pulley. Run it upward to accessory pulleys, one by one, as shown on the belt-routing diagram. Don’t put it on the tensioner pulley until you’ve routed it around all the rest. Check the serpentine-belt routing diagram at each stage of this step.
Reconnect the belt-tensioner tool to the serpentine-belt tensioner. Move the tensioner out of the belt path just as you did before. Move the new belt over the tensioner pulley with your other hand. Hold the belt to the pulley as you slowly move the serpentine-belt tensioner back into position. Take the tool out and close the bonnet when done.