One problem related to engine rattling and whining sounds has been reported for the 2013 Mercedes Benz C250. The most recently reported issues are listed below.
When the vehicle is stationary, it takes four clicks to turn over. After turnover, it idles rough, and makes a rattle noise around 1500 rpm. Mercedes ran a diagnostic and said it was a p034062 code and recommended replacing camshaft adjusters and camshaft adjuster magnet and seals. The cost was $4500. This is a very common problem in these mercedes and I believe their should be a recall as this could cause engine damage while driving or pose a significant safety issue.