One problem related to water pump has been reported for the 2009 BMW 335. The most recently reported issues are listed below.
Vehicle in straight, forward motion at highway speed (approx. 60mph) and engine power is reduced dramatically. Reaching a safe resting area posed significant risk due to lack of warning or descriptive vehicle fault. Smoke and/or steam emitting from engine compartment. Cause appears to be faulty electric water pump at 56,000 miles/5 years in service. Second occurrence.