How to Replace a 1990 Mercedes 300Sl Engine Belt


1. Open the hood and locate the belt routing diagram. The routing diagram for the 1990 Mercedes 300Sl is located on the fan cover. This diagram will be needed to install the new engine belt.
2. Remove the fan cover by unscrewing the screws on both sides of the cover with a flat-head screwdriver. Pull the cover off and place it on the ground.
3. Locate the spring-loaded belt tensioner on the front of the engine. The tensioner device for the 1990 Mercedes 300Sl models is located on the front center of the engine. Use the bolt in the middle of the tensioner device pulley to rotate the tensioner.
4. Rotate the tensioner pulley counter-clockwise with the breaker bar and a metric socket. Then, slide the belt out from around the tensioner pulley. Release the tensioner and remove the breaker bar.
5. Slide the belt out of all of the accessory pulleys and out of the engine area. Then, slide the new belt into the engine area and around each accessory pulley as instructed by the routing diagram.
6. Rotate the tensioner device pulley counter-clockwise again. While holding the tensioner over with one hand, slide the belt around the tensioner pulley with the other hand. Release the tensioner and it will tighten the belt as it retracts. Inspect the belt to make sure that it is fully seated in all accessory pulleys.
7. Crank the 1990 Mercedes 300Sl and inspect the belt as it travels around the moving pulleys to make sure that it remains seated with the motor running. Then, turn the motor off and reconnect the fan cover back over the fan. Close the hood.