Two problems related to engine noise have been reported for the 2008 BMW 328. The most recently reported issues are listed below.
March 14, 2014. While starting the car, I heard a laud snapping sound coming from the engine compartment at passenger side. A moment later when taking a left turn I heard another strange noise form the same area. After that the engine started to sound differently with a small noticeable vibration. Turns out that all 4 engine mount bolts on the passenger side were snapped. It cost more than $1000 to fix it. This was very unexpected.
While driving a loud bang was heard. The car made noise after that driving it. The car was then taken to the dealership, and upon examination it was discovered the mounting bolts ( aluminum ) for right engine support arm broke. They were replaced by the dealership as they said it was a flaw in the engine bolts. The car had 40,984 miles.