How to change serpetine belt on Mercedes Benz 190E?

Loosen 19 MM stud centre belt tensioner. Then loosen 13 MM Sleeve nut that adjusts the belt tensioner (nut is located between distributor & Power Steering resovoir) make sure tensioner is fully retracted. you shold be able to get old belt off .But may have to get more slack by removing bottom alternator bolt.Assembly is reverse procedure.