A serpentine belt, also known as a multi-rib or poly-v belt, is a drive belt that runs multiple components in a vehicle's engine. ... The serpentine belt employs an automatic tensioner that adjusts ...

Despite doing so much, most of us forget the serpentine belt even exists — let alone that its tension matters. But it does. A lot. Too tight and it'll grind bearings to dust. Too loose and you ...

Spring-loaded automatic tensioners are the most common today, introduced in the mid-1980s. They use a coil spring to apply constant tension and usually self-correct for minor belt stretch over time.