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Accessory Belt Tensioner

I have seen some tensioners that have indicators on them letting you know they have worn and no longer meet specs. On the tensioners with no indicators, is there some rule of thumb for replacement? ie…time, mileage, environmental factor, day of week, color of car, etc.?

The only tensioners I am familiar with have no indicators. It in my guestimation is a spring loaded device with a wheel and bearings. If the bearings go out, you will hear it, if the spring fails you will know it, by bad belt tension. I guess in my book it is a play it by ear kind of thing.

Here’s a good tutorial from GATES that shows when the serpentine belt tensioner should be replaced.


Some people use 100k miles as a guide.
I know my bearing was dry at 125k.
Better safe than sorry.

The video in the link from Tester shows how a worn-out tensioner behaves. I suspect that the wear indicator on the tensioner is for the belt, showing when the belt has stretched and needs to be replaced. Although, it’s possible that if a belt stretches beyond specifications, the tensioner may have overextended and been damaged.