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As you may have guessed by the name, the crankshaft pulley works in close proximity with the crankshaft. The crankshaft takes power from the engine to move the wheels, transforming the pistons’ linear motions into rotational ones. The torque applied to the crankshaft during this process can cause a lot of stress and vibration, ultimately causing it to break or resulting in damage to other engine parts. The crank pulley, also called a harmonic damper, is in charge of dampening and absorbing these vibrations.

It is a mechanical system made of a steel or cast-iron hub and rubber fibres, which sits between the crankshaft and accessory belt. The rubber is responsible for the shock and noise absorption, and its location at the accessory belt is important for its second job: to bring power to other car components like the alternator and the power steering pump and to make sure the various parts run in unison. 

Why does the crankshaft pulley fail?

While the crankshaft pulley seems like a small part of your car, it is actually quite significant and the well-being of your crankshaft and many other components depend on it.  
Over time, the crankshaft pulley can wear out or even crack from old age, temperature changes, or exposure to chemicals. It is important to have the crankshaft pulley replaced before it can damage other parts of your car, which could result in more expensive repairs. This can include damage to the transmission by unabsorbed vibrations. If this continues over a longer period the bearings and gears of your car can be damaged, which is very expensive to fix.
If you notice one or more of the symptoms listed below, you should take your car to a garage nearby to have the crankshaft pulley replaced if needed. 

Bad Crankshaft Pulley Symptoms

• The first thing most drivers notice when the crankshaft pulley is about to fail is increased engine vibration. Since the harmonic balancer is responsible for absorbing those vibrations, a sure sign of the problem is noise from the crankshaft pulley and a shaking of the engine at higher speeds. 
• Since the crankshaft pulley is in charge of powering the alternator, you might notice lights flickering or not working at all if there is a problem with the pulley.
• Another symptom of a faulty crankshaft pulley can be an issue with the power steering pump. Since the transmission of power steering fluid depends on the pump, chances are the crankshaft pulley is to blame if steering becomes difficult.
• You may also notice irregular engine speed when your engine is idle if there is a problem with the crankshaft pulley.