Genuine BMW idler pulley for the S50/S52 inline-six used in the E36 M3 (and shared architecture on other E36/Z3 six-cylinder engines). Runs on the water pump/alternator drive belt and keeps proper belt tension and alignment; worn idler pulley bearings are a common source of a chirping or rumbling noise from the front of the engine, and replacement restores quiet, reliable belt operation.

Fitment: BMW E36 M3 (S50/S52) and Z3 M Roadster/Coupe (E36/7, S52) (confirm exact belt-drive configuration at checkout).