Hey Rob, the vehicle in question has an automatic belt tensioner. It can't be tightened. Yamil78, is the P/S fluid at the correct level. Make sure it is before you do anything else. Also, have you had the car to an MB dealer? 210's are notorious for a variety of steering noises. Sometimes the column rubs the firewall boot/grommet(easy fix). Sometimes it's a pressure noise that requires replacement of the steering rack. In this case, the noise is usually worse in cold weather. I've seen both cases dozens of times.