Ringing or Rattle Durning Warm Up Cycle (Youtube Link)
 

I recently purchased a 2012 cts 3.6 AWD with 60,000 miles. The car runs fine, but the past week on cold starts I have noticed a ringing or a rattle from the engine compartment that persists throughout the warm up cycle. I have brought the car to the dealership, dropped it off the night before to ensure they hear the same noise in the morning. However they claim to hear nothing. Take a listen and please let me know any opinions. I know 2008 and older suffered chronic timing change issues, not sure if this noise is indicative of timing chain stretch.


Thanks!