The serpentine belts will get "glazed" and tend to squeak from time to time. When the bearings go it is usually a noise that is continuous. You will use the longer of the TWO belts listed for the W22 chassis with the 8.1L engine. Since you will need to replace the belt, it is not a bad idea to replace both the idler pulley AND the tensionor pulley. This is not a really difficult job to do but it does need to be done from the top for the idler pulley and from the bottom for the tensionor and belt change. I've change the belt at the side of the road. Takes about 15 minutes to do. I would get a Gates belt instead of the cheaper Dayco belt. It will last longer.