What causes crankshaft pulley noise?

[MiguelDella]

Crankshaft pulley noise is due to excessive axial clearance. Axial: Excessive axial clearance can cause the car to jerk forward and backward when starting, sometimes accompanied by metal impact sounds; Diagnosis: Use a pry bar to move the crankshaft pulley under the car to check for clearance; Cause: Worn-out crankshaft thrust washers require replacement. Radial: Metal impact sounds may be heard during acceleration or deceleration, accompanied by engine vibration. Diagnosis: Use a stethoscope (automotive repair stethoscope or a 2-3 foot long copper pipe/iron rod) to listen. If the above symptoms occur in the lower part of the engine, proceed with further inspection by draining some engine oil to check for metal shavings. If present, there's a 90% chance the noise is caused by excessive crankshaft bearing clearance. If conditions permit, removing the oil pan will provide a more accurate diagnosis.