The OEM S54 Solenoid Coil pack is known for failure due to a number of reasons – one of these is failure of the sealing plate seals between the main Vanos unit and the solenoid unit.

The cause of this failure is the cheap rubber that BMW uses not being suitable for the engine environment. Failure can result in poor oil pressure, poor pressure regulation and oil leaks.

Information and replacement procedure can be seen here.

BS024 required when installing BS023, but can also bring big benefits alone.