Upon purchasing a used Volvo, always remove the serpentine belt and inspect all pulleys by hand. Don't wait for problems to happen, this is a 10 minutes check. The alternator one also needs be inspected at the clutch
https://m.youtube.com/watch?v=a_Pzmj0jxfw
If parts have been replaced just before the purchase, look carefuly for the brands used and replace any low cost brand with a quality part.
This is even more critical on the D5 engine, just like in the story above. Without exception, a failed serpentine belt on a D5 engine means the end of the engine.