Timing chain failure is a major failure of the N47 engine. Most BMW Indys will tell you this. Last week my local indy had an 08 plate 1 series with a snapped chain (smashed engine) and just finished a rebuild on a 520d too. Watch out for a rattle on idle that doesnt clear until after 2000rpm or so.
E90 330d - N57
Prof Nav - 6FL - Visability Pack - Alpine Hi-Fi Upgrade - L7 Subwoofers - L7 rear mids + tweeters - 6FL