How to Install a Mercedes Belt Tensioner

1. Locate the square hole in the tensioner arm, and place a 3/8-inch ratchet into the square hole. Pull up on the handle, and remove the belt from the tensioner pulley.
2. Remove the tensioner spring from the tensioner arm, using a pair of pliers.
3. Remove the two bolts that secure the tensioner arm to the engine block, and pull the tensioner out of the engine bay.
4. Secure the new tensioner arm to the engine block, using the socket and the ratchet.
5. Reconnect the tensioner spring to the tensioner arm, using the pliers.
6. Lace the ratchet into the square hole on the tensioner arm. Pull up on the ratchet handle, and place the belt over the pulley.