190D 300D 300SD 300SDL 350SD Belt Tensioner Shock

This is the number one cause of a sharp engine rattling noise at idle on the early 602, 603 and 604 engines. It is not that the shock goes bad, but the bushings car wear out prematurely due to harsh vibration and the ends of the shock will make a terrible noise inside the loose bushing. To test hold a block of wood down hard on the end of the shock while the engine is running to see if the noise goes away.