I needed to replace the alternator on my 2011 c300 so I replaced the belt, tensioner and pulleys. A few days after installation, the belt started squeaking, which made me angry. I removed the belt and smooth surface idler pulley and found that the steel wire in the belt was touching the pulley wall. Basically, this belt wasn't straight and had a point where it was wider, causing the belt to be tight against the pulley and causing noise. I ordered this as a replacement and it is slightly narrower than the previous belt. Pay a few dollars more to get this belt instead of the standard continental belt.
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