Located at the front end of the crankshaft, the crankshaft pulley is what drives the alternator and other engine components. The crankshaft pulley is also called a harmonic balancer, and is a visible wheel mounted to the crankshaft.
The crankshaft pulley is responsible for turning the belts that operate the engine and other accessories. It holds a serpentine belt or separate belts for the air conditioner and alternator. Unfortunately, this pulley can become faulty over time and may need to be replaced.
Symptoms of a faulty crankshaft pulley include non-working engine accessories or a loud knocking noise. Before replacing the pulley itself, it may help to check out the rubber insert located between the center and outside sections of the pulley. This rubber insert may become worn or damaged and cause timing problems or other symptoms. Sometimes, the crankshaft bolt responsible for securing the pulley to the engine may become loose; a repair requires nothing more than tightening this bolt.
Drivers should routinely check the crankshaft pulley and its belts for signs of wear or damage. Although it is not recommended that novice mechanics take on the task of replacing the pulley, it is usually a simple task for seasoned mechanics.