Belt tensioners are basically made up of the following parts: Tensioner Arm: This part is attached to the tensioner pulley, which applies tension to the belt. Tensioner Pulley: This is the part that rotates and applies tension to the belt, typically by the use of a spring or hydraulic system. Spring or Hydraulic System: This component is in charge of keeping the belt taut. A coiled spring provides tension in a spring-loaded tensioner, whereas fluid pressure is employed to maintain tension in a hydraulic tensioner. The tensioner assembly is attached to the engine block by this component. Bearings: To enable smooth, low-friction rotation, the tensioner pulley, and arm are frequently mounted on bearings. Dust Cover: Dust covers are used on some tensioners to protect the pulley and bearings from dirt and debris. These are the fundamental components of a belt tensioner. Depending on the brand and kind of tensioner, the specific design and components may differ