I have the same noise in my 2010 320d with 41,000km on it.
I will be taking the car in for inspection next week, but not really sure if i should give the go for dismantling the entire engine (if the dealer should say that's the case), as i talked to two other guys who did the operation, just to get the noise back soon after (2-3months/5000km after). They have been using the car like that ever since, without any other problems.
I really think it's just the way this engine sounds and there's nothing to worry about. After all, a timing chain will make more noise than a belt.
BMW 320 dA LCI, BMW PPK - 197HP, 2010, sapphire black, steptronic
Last edited by EQUANT; 11-25-2011 at 04:07 PM.