Common NoisesThe first clue that it's time for serpentine belt maintenance is usually noise— a loud squeaking or squealing right after you start your engine or park, while the engine is idling. You might also notice:
A whining or growling noise when you accelerate. This is usually caused by misalignment.
A buzzing noise. This is likely an overrunning alternator decoupler failure
An inconsistent chirp. This can usually be contributed to a misaligned or worn out belt or pulley.
A sharp squealing noise. This might be low tension or pulley drag.If you start to hear any noise coming from your engine bay, you should make an appointment with your mechanic for maintenance right away.
Signs of Uneven WearThe second tell-tale sign that it's time for serpentine belt maintenance is uneven wear. Belts are made up of a flat surface running through the middle, the rib, and edge portions called flanks. All portions of a belt should wear uniformly. If you start to hear strange noises or start to smell burning rubber wafting from the engine, pop the and examine your belts for:
Rib wear. This is common with belts nearing the end of their usable life, but can also be caused by misalignment or defective pulley bearings. Either way, it's worth a visit to the shop.
Cracking. This is usually caused by age or improper tension, both of which stretch the belt farther than comfortable. A cracked belt should be replaced as soon as possible—a crack can quickly turn into a tear and cause the belt to slip or a snap.
Glazing. Like the image shown above, the shining and hardening of a glazed belt is usually due to aging—if the belt can't get a proper grip on the pulleys, it can have a devastating impact on engine performance.
Pilling. Pilling on the belt can be caused by a host of issues—misalignment, low tension, worn pulleys, fluid contamination, or a combination of these. Either way, the belt will need to be adjusted by a professional.
Backside damage. If you look at the pulley-side of the belt and notice any of the above symptoms, you're most likely dealing with a defective pulley or an improper installation.
Read more: Common Serpentine Belt Problems & How to Fix Them