The GMC 4.3 liter V-6 engine began using serpentine belts in the early 1990s, and these systems require a tension pulley. This pulley can wear out and need replacement. The average backyard mechanic can remove a tension pulley in about ten minutes.
Check the pulley for damage or problems. The tension pulley is a loaded spring device and can cause injury if it is removed when damaged. If a pulley is suspect, defer to a shop for removal.
Remove the belt from the pulley. The 4.3 liter tension pulley is on the lower passenger side of the motor, in the front. Press against the pulley; this will loosen the belt enough to remove it.
Unbolt the pulley from the engine by turning the center bolt counter-clockwise. A short socket is required because there is not much clearance from the pulley to the fan shroud and fan. Once free, the pulley will slide off and away from the motor.
Replace the pulley with the new one and bolt it back onto the engine, with the pulley arm to the left. There is a groove present that will accommodate the pulley flush when it is positioned correctly. Once it is bolted in, replace the belt by pressing on the pulley and looping the belt over it.
