One problem related to loud engine noise has been reported for the 2013 Mercedes Benz C250. The most recently reported issues are listed below.
Intermittent "inoperable mode" illuminated since mileage 41974. Car decelerated on the highway from 75mph to 10mpl nearly causing an accident. Pulled over, turned off vehicle, was completely shaken up. Waited about 5 minutes, restarted and it was normal. This has happened 13 times in the 6 months of ownership. Dealer was unable to duplicate issue. Vehicle again duplicated the same problem, I made a left turn, attempted to accelerate on a city street and it began showing the "inoperable mode" and check engine light again. A month later, the engine was making a loud noise like rocks in a dryer. Pulled over immediately away from traffic. I contacted the dealer, they said to "drive it in". On the way, the car broke down. Called mercedes customer care, they sent a tow truck. Car is under warranty until 50k, and is at 49404. While my 2013 C250 is in the shop, they issued me a 2016 c300 with less than 550 miles on it. After driving for only 5 days, it also has the check engine light and says "collision prevention assist plus inoperative". I notified the service advisor and he will not return my messages to have another vehicle issued. This is clearly a manufacture defect that mercedes is blatantly ignoring. This is stressful and heartbreaking that I have owned the vehicle 6 months, with a mountain of "manufacturer warranty" issues, they are asking me to pay the $2500 if it is deemed "not warrantable". So I am supposed to trust mercedes to be honest at this point? the only contact I have received since is that they will be charging me $2595. 00 in labor to disassemble my engine so that they have a "concrete answer" as to if my vehicle will be warrantied. It is under warranty and all services have been done as mercedes advises. For mercedes to not warranty it would be a direct violation of the manufacturer warranty and further prove their negligence.