A crankshaft pulley is an engine component that serves to drive a number of other components by way of the drive belt. The pulley is fastened to the end of the crankshaft where the shaft protrudes through the lower front wall of your engine.
Your engine houses a number of pistons that pedal the crankshaft like your legs pedal a bicycle. As each piston rises in its cylinder to compress a mixture of air and fuel, a spark plug ignites that mixture and causes combustion inside the cylinder. The rapidly-expanding gases that result propel the piston downward against an offset protrusion on the crankshaft, the rod bearing journal. Each piston does its job in a series of upward and downward motions to turn the crankshaft and produce power.
As the crankshaft turns, the pulley attached to the end drives a belt to operate components such as the alternator, AC compressor, power steering pump, and sometimes the water pump. On some engines, the crankshaft pulley is integrated with a harmonic balancer that serves to balance the rotation of the crankshaft.
To replace a crankshaft pulley, a technician will have to remove the drive belt from the front of your engine. On some engines, the pulley can be accessed from above, while others need to be accessed from below. If from below, the technician must raise and support your vehicle for access to the pulley. Shields and guards will need to be removed from the underbody. On some vehicle makes and models, it might be necessary to remove the cooling fan assembly or even drain and remove the radiator as well.
From there, with access available to the lower face of your engine, a technician will need to remove the large crankshaft bolt that holds the pulley in place. A special pulling tool is needed to unseat the pulley from the crankshaft. This tool can differ from one engine to the next, and attention must be paid to prevent damage to the harmonic balancer if your engine is so equipped.
Once the pulley has been removed, the new pulley is installed in its place, complete with a new crankshaft bolt torqued to manufacturer’s specifications.