Originally Posted by
TurboMedic
Yes, mine is a gen2. They upgraded the timing chain layout (2 chains instead of 1 with new tensioners) to mitigate the cold start rattle from the chain stretch, which sounds ENTIRELY different if you actually hear a gen 1 with a stretched chain. It sounds awful. The sound these make is a rattle I describe as a mechanical indexing sound which is brief, has defined start and stop points, and irrespective of RPM sounds the same. Its easy to replicate, running cold you can either blip the throttle in P, or when driving slowly forward lift your foot off the throttle and you'll hear it until 57-60c and its gone. The BW phasers are likely making the noise when they're shifting position. There are a number of random theories on the US boards, but of course they can all run back and get buy backs and there are a ton of chicken littles out there. I believe there was an ECM update that reduced this noise as well for a while, likely by altering the VVT strategy in cold operation.