What causes crankshaft pulley noise?
3 Answers
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.
A crankshaft pulley noise may sound scary, but the common issues are easy to understand. Having driven for over a decade, I've encountered all sorts of noises—most often a squeak from worn wheel bearings or friction sounds from a loose belt. Once, my car made a rattling noise, which turned out to be a frayed belt rubbing against the pulley edge. I immediately pulled over to check, popped the hood, and listened for the source. If the noise worsens when revving in place, it's likely a bearing issue; belt problems are usually more noticeable at low RPM. Don’t delay—fixing it early by replacing the bearing or belt is simple. Otherwise, a snapped belt can disable the alternator and AC, leading to costly engine damage. Inspect the belt every 50,000 km and replace it in time to avoid such headaches. Keeping a spare belt in the car is also a good idea.
I just bought a car not long ago and don't understand much about technology, but once while driving I heard an abnormal noise from the crankshaft pulley, like a metal scraping sound, which made my heart race. Simply put, it could be due to a loose pulley or a damaged bearing causing vibration and noise, or insufficient belt tension leading to slippage and noise. As a beginner, it's important to be cautious—first try driving at a slower speed to see if the noise changes, and definitely avoid driving at high speeds. Safety comes first. Quickly check under the hood to see if the belt is loose or cracked, but if you're unsure, don't touch anything and go straight to a repair shop. Delaying repairs could lead to the belt breaking and damaging the engine, resulting in expensive repairs. Usually, pay attention to the engine sounds; addressing issues early can save you trouble and money. Regular maintenance checks can prevent unexpected problems.
