The 1999 Pontiac model vehicles that came equipped with the V-6 engines included the Firebird, Bonneville, Grand Am, Grand Prix and the Montana. All of the Pontiac models have a serpentine belt that controls the front engine accessories. The serpentine belt is tensioned to each accessory pulley by a automatic belt tensioner. The tensioner keeps the proper tension on the belt while the engine is running. Replace the belt if it becomes damaged or has a lot of cracks on the inside.
Park the Pontiac in a safe work area and open the hood.
Inspect the top of the black plastic cover that surrounds the fan for the serpentine belt routing diagram. This diagram has the instructions for installing the new serpentine belt around the accessory pulleys.
Inspect the front of the engine and locate the automatic belt tensioner. The tensioner on the 1999 Pontiac model vehicles is located between the alternator and the crankshaft pulley. The tensioner has a pulley on one end with a bolt head in the center of the pulley. Use the bolt head to rotate the tensioner.
Turn the tensioner counterclockwise with the breaker bar and a metric socket. Pull the belt out from under the tensioner pulley with your other hand. Then, slowly let the tensioner retract until it stops.
Pull the belt out of the other remaining pulleys. Then, pull the belt out of the engine bay and lay it on the ground.
Route the new belt around the crankshaft pulley. Then, route the new belt around the other remaining pullleys by using the serpentine belt routing diagram for instructions.
Rotate the tensioner pulley counterclockwise with the breaker bar and socket. Then, slide the new belt under the tensioner pulley. Slowly let the tensioner retract until it stops. The tensioner pulls all of the slack out of the belt and brings the new belt to the proper tension. Remove the breaker bar and socket from the tensioner pulley.
Inspect the new belt to ensure that it is seated inside of all the accessory pulleys as directed by the diagram. Then, crank the engine and allow it to run for about 15 seconds. Turn the engine off. Inspect the belt again once more to ensure that the belt is still around each pulley. Close the hood.
