Locate the tensioner pulley for the serpentine belt. It is usually a black or silver-colored metal pulley with a spring-loaded arm attached to it.
Loosen the tensioner pulley bolt using a wrench or socket set. This will release the tension on the belt.
Once the bolt is loosened, use a pry bar or other suitable tool to pry the tensioner arm away from the belt. This will create more slack in the belt.
Reposition the belt around the pulleys as needed, making sure that it is routed correctly and that all of the pulleys are engaged.
Once the belt is in the correct position, slowly release the tensioner arm and tighten the bolt. This will put tension back on the belt.
Check the tension of the belt by pressing down on it with your thumb. The belt should deflect about 1/2 inch (1.3 cm) under moderate pressure.
If the belt is too tight, loosen the tensioner bolt slightly and pry the tensioner arm away from the belt until the desired tension is reached.
If the belt is too loose, tighten the tensioner bolt until the desired tension is reached.
Once you are satisfied with the belt tension, make sure that the tensioner pulley bolt is tightened securely.
Start the engine and check for proper belt operation. Listen for any unusual noises or vibrations, and make sure that the belt is tracking correctly on all of the pulleys.
If everything seems to be in order, you have successfully adjusted the belt tension on your 1999 Malibu V6.
