It’s possible that the previous owner didn’t put the proper number of shims in there and now the fan is being shredded. Made that mistake myself, cost a grand to fix. To check, pull off the half-pulley and look at the fan where it slides over the alternator shaft. Also count the number of shims - should be six total, if memory serves. Tension is increased or decreased based on what side of the half-pulley they’re installed on.
Got some pics from my experience with that here
