This document discusses why a BMW engine may overheat when idling and what actions to take. Common causes of overheating at idle include a faulty radiator fan, a clogged radiator, a defective thermostat, low coolant level, or water pump failure. These issues can prevent proper coolant circulation and dissipation of engine heat. The document recommends checking the coolant level, radiator fan, radiator, and thermostat if overheating occurs at idle. If problems are found, the vehicle should be taken to a service center for repair.