How did you get the belt off without removing the fan clutch?

To get the fan clutch off you need about a 1/4" dia rod, bent at a 90 degree angle for the last 1/2" of it or so. This goes in behind the fan clutch pulley, engages into a groove cast into the fan bearing bracket, then into a hole in the pulley flange. This keeps the fan pulley + fan clutch from rotating when you take an 8mm allen wrench (or short socket) to the bolt holding the fan clutch on the front side. Then the fan clutch will come off.

I suspect your problem is not with the fan clutch, but instead with a worn fan bearing. You might be able to get the bearing replaced, or you might have to shell out for the whole fan bearing bracket.

Mercedes makes two "special" tools for removing the fan clutch - one is a rod bent at the right angles, one is a very short 8mm 3/8" allen-head socket.