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Serpentine Belt too tight?

Recently after replacing the serpentine belt in my 1992 MB 300TE 4matic, the bearings on the air pump failed. The new belt seems pretty tight, with no slack. Is it possible that an overly tight belt could lead to damage of the air pump bearings?

If there’s a spring loaded tensioner for the belt, then no. But I can tell you what might have happened. When bearings are imposed under a side load as from a belt, they stay pretty happy. It’s when this side load is removed, and then the bearing rotates from installing the new belt, the bearing rollers/balls move to a different position when the side load is reimposed. And this can make the bearing very unhappy, and it fails.


Thanks for your reply. It sounds like it would be difficult to avoid this problem, particularly in older vehicles that are more susceptible to failure. My car has 208,000 miles and the air pump is original equipment.

Are you saying the tensioner can not rotate when a new belt is installed? What kind of sloppy engineering is this? It is impossible to install a belt without moving the tensioner wheels, 2 on e 320. Am I right?