Technicians facing engine noise and vibration problems on BMW diesel engines are being urged by Schaeffler’s REPXPERTs to check the solid pulley on the front end auxiliary drive (FEAD) system, and to replace it with an INA overrunning alternator pulley (OAP) where possible.

The FEAD system provides power to an increasing number of engine functions, with each driven function adding extra strain on the belt system. Workshops have reported seeing BMWs displaying the symptoms of this strain in increasing numbers.

“Engine designers are relying on increasingly complex auxiliary belt systems to provide power to critical components,” said Alistair Mason, Technical Services Manager at Schaeffler REPXPERT.

“Unfortunately, a solid alternator pulley will not absorb the constant rotational irregularities coming from the engine, or sufficiently prevent them either. This is especially true in diesel engines. Ultimately these vibrations can damage the entire drive system, creating noise and vibrations that can be heard and felt by the driver.”

The problem can be fixed by upgrading the FEAD system to include an INA OAP. This is a particularly suitable option for BMW diesel engine cars manufactured between 2004 and 2011.

“Even though it is not the originally fitted component, significant improvement can be made by swapping out the original solid pulley for an INA OAP,” said Alistair. “This will smoothly disengage the FEAD from the rotational irregularities, rendering the engine quieter and improving drivability.”

Just three INA OAP references cover BMW’s 1, 3, 5, 6 and 7 Series passenger cars, as well as the X1, X3 and X5 equipped with the 1.6 and 2.0 M47 and N47 diesel engines, and the six cylinder 2.5 and 3.0 M57 and N57 diesel engines.

Schaeffler encourages aftermarket professionals to stay updated with its latest news by regularly checking the REPXPERT app, or by visiting the website at: www.repxpert.co.uk.