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Perhaps the easiest way to re-find these posts is to search on my screen name "DanielW". That should pull up my recent posts I believe the tensioner idea is one of the first entries which will come up.
As to the fan rubbing the tensioner pulley (the one directly under the Water Pump pulley), I think there are two possible reasons which might allow these parts to touch. 1. the fan clutch has a lot of play in it, and must be replaced. 2. the belt tensioner is shot and must be replaced. The tensioner is a rubber bushing which is twisted to provide belt tension. Over time and heat they break down and must be replaced. One reason they break is that the shock or shock bushings go bad first and this allows too much movement for the tensioner unit to absorb.
Dissembly will allow you to diagnose the situation. Start with drain and remove the radiator. Then, with a suitable tool remove, (search under fan clutch or water pump), the fan clutch, and belt. At that point you should be able to see what is broken, and can order the needed parts. Fastlane here has good prices if you are going to DIY.
E-Mail me back if you need additional help. The search function may help with other Questions from this vast archive of helpful MB owners.
Luck to you,