What are the causes of tensioner pulley noise?
2 Answers
Tensioner pulley noise can be attributed to the following reasons: Faulty torsion spring: Normally, the spring has significant tension and cannot be twisted by hand. If it can be easily twisted, it indicates damage. Once the spring fails to provide sufficient tension, the belt will vibrate, resulting in noise. Bearing deformation: The tensioner pulley rotates at high speed during operation. If the bearing becomes deformed or the lubricant leaks, the pulley will vibrate at high frequency, causing abnormal noise. Loss of belt elasticity: The belt is a rubber product, just like tires, and has a service life limit. Over time, the belt becomes hard and brittle, leading to less smooth operation. This causes the tensioner pulley to vibrate, which is another source of noise.
After running this auto repair shop for so many years, I've seen plenty of cars with tensioner pulley noise issues. The most common cause is worn-out bearings—when the lubricating grease inside dries up, it creates a squeaking sound. Another issue is incorrect belt tension: if it's too tight, the tensioner pulley bears excessive pressure and produces a high-pitched screech; if too loose, the belt slips and causes friction noise. I once encountered a case where the owner installed the tensioner pulley themselves but misaligned the screws, causing the entire pulley to wobble and make a clunking sound. If the belt is old and cracked, it can also create abnormal noises when rubbing against the tensioner pulley. The most typical scenario is a screeching sound during cold starts, which usually points to belt or tensioner pulley problems. When replacing parts, it's best to change the entire belt set—just replacing the tensioner pulley might not solve the noise issue. I always remind car owners not to delay repairs, as severe noise can wear down the belt and lead to a breakdown on the road.
