I'm new to this forum and own a 2010 C300 4Matic. I'm posting here in hopes that others will read this who have had similar mechanical issues with their cars and take a few minutes to file a complaint with NHTSA. The goal here is to have enough people with issues to actually take the time to file a official complaint that might lead NHTSA to force Mercedes Benz to issue a recall of the vehicles. I believe this issue affects mostly the W204, 2008-current models, but it's possible other generations might be affected as well.
Last week the belt tensioner on my vehicle seized up causing the serpentine belt to shred, as well as causing damage to the upper and lower pulleys. The vehicle has about 73,000 miles on it. After doing some quick search online, it seems that this is not an isolated issue, but rather a widespread issue with this vehicle. I've read some owners have had this failure with as little as 15,000 miles and so forth. Obviously mine is out of warranty and got stuck with the bill. The average repair cost for this issue in the northern NJ area is running around $650-$850 at the dealer.
Whether your vehicle was repaired under warranty or you had to pay out of pocket for this repair, please take the five minutes to file a complaint with NHTSA. This is the only way to have MB to issue a recall. And if you think it's a waste of time to file a complaint, take a look at the latest recall for tail lights on the C Class. It was issued because there have been several dozen complaints with NHTSA, thus forcing a recall of the C Class for tail lights.
I was very lucky that the belt tensioner seized up after I pulled into a parking lot. If this had happened when I was driving on the highway, there is no doubt that it would have caused a very serious accident (since you lose power steering amongst other accessories as well).
When I spoke with Mercedes Benz customer service, they said they are not aware of any "known" issues and there is nothing they can do about it, but the forums online speak otherwise.
Please go here to file a complaint (have your VIN number ready as it is VIN specific):