Just bought a 2015 Q7 TDI with 50k miles a few weeks ago. I noticed what I believe to be a timing chain rattle on cold start. Is this normal? Is there an oil check valve that needs to be replaced or does the timing chain tensioners need to be replaced? Very concerned with it at such low mileage. Any insight would be appreciated. I also have an A6 with the same motor and never hear this on startup.