The belt tensioner in your 5.9L Cummins is responsible for keeping constant tension on the belt to ensure vital engine components such as your water pump, alternator, and power steering pump are working properly. A failing belt tensioner can have a couple different symptoms. The tensioner can lose its tension allowing the belt to become loose and eventually ejecting itself or, the bearing can fail not allowing the pulley to spin causing a squeal noise from the engine bay. Replace your failed tensioner with a genuine Cummins Replacement Belt Tensioner Assembly. This tensioner is a direct replacement and uses the factory hardware for isntallation.