What they do
The serpentine belt is one long belt that the engine spins to run the alternator, the A/C compressor, often the power steering pump, and on many engines the water pump. The tensioner is a spring-loaded arm with a pulley that keeps the belt tight.
Common symptoms
- Squealing, especially on startup, on cold or wet mornings, or when you turn the wheel or turn on the A/C
- Chirping from the front of the engine
- Cracks, missing chunks, frayed edges or shiny, glazed ribs on the belt
- The tensioner arm bouncing or shaking while the engine runs
- Grinding or rumbling from a pulley
- The belt riding off the edge of a pulley, or coming off
What to look for
- Engine off: look over the belt for cracks, chunks, fraying and glazing.
- Engine running: watch the tensioner arm from a safe distance. It should stay mostly steady. Keep hands, hair and loose clothing away from the belt and fan.
- Pulleys: with the belt off, a mechanic spins each pulley by hand. They should turn smoothly and quietly.
Could be something else
A squeal or grind can also come from a bad bearing in the water pump, alternator, A/C compressor or power steering pump. Rule out the belt first.
Is it safe to drive?
If the belt breaks, the alternator stops charging, power steering gets heavy, and if it drives the water pump the engine can overheat fast. Don't ignore a squeal. It's smart to check the belt, tensioner and pulleys together, since one worn part wears out the others.
Related: Bad water pump symptoms · How your alternator works
Think it's your belt or tensioner? Northwoods can check it right where your vehicle sits, anywhere in the greater Twin Ports area.