2000 e430 mercedes serpentine belt won't fit after new tensioner installed

  mercedes/e-class/1996-2003

My Belt tensioner recently destroyed itself. It actually came completely apart and the pulley ended up in pulley never never land. I purchased a new belt tensioner on-line and installed it yesterday. I checked the serpentine belt and it was in fine shape so I planned on reusing it. The new tensioner had the pin installed when it arrived so I assumed, install the tensioner, install the belt, release the tensioner pin and we'll be in business. The reality: I installed the new tensioner, and attempted to install the belt but it was too short. I checked and rechecked the routing of the belt and how it was seated on the pulleys and all is fine, but it just doesn't fit. I have just learned there have been modifications to the belt tensioner and the pictures indicate the old tensioner pulley to be smaller than the new replacement. Does this mean a new and different belt? I talked to the local dealership and while they tried to be helpful they were as confused as I am. Any help/advice would be greatly appreciated.

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