Posted on 2/27/2026
A quick squeal right when you start the engine is one of those noises that feels small, but it tends to get your attention. Sometimes it is just moisture on a belt, and it goes away in a second. Other times it is the first hint that a belt, pulley, or accessory is wearing out. The best clue is when it happens and how long it lasts. Common Squeal Sources On Cold Starts Most startup squeals come from the belt drive system, which is the belt and pulleys that spin components like the alternator and A/C compressor. When the engine first fires up, the belt has to grab quickly and transfer power right away. If traction is poor, you hear that sharp squeal as the belt slips for a moment. A squeal can also happen if an accessory is dragging more than normal. A weak alternator bearing, a stiff A/C compressor, or even a worn idler pulley can add resistance. That extra load makes the belt work harder at the exact moment it is cold and less flexible. Serpentine Belt Gla ... read more