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How to Replace a Drive Belt on a 1985 Mercedes 380SE

The 1985 Mercedes 380SE comes equipped with one single drive belt that is called a serpentine belt. The serpentine belt controls all of the engine accessories at the same time from just one belt. The belt is routed around all of the accessory pulleys in a certain direction. The belt also has a routing diagram that gives the instructions for the routing process. When the motor is running, the belt is driven around each accessory pulley by the crankshaft pulley. Replace the belt if there is excessive wear or cracking present anywhere on the belt.

Tools Used: 3/8-inch drive breaker bar, Metric socket set, New belt

Replace Drive Belt

Park the 1985 Mercedes 380SE and open the hood.

Locate the belt routing diagram on the base of the fan shroud. The diagram is a picture of all of the accessory pulleys with the belt routed around each pulley in a certain direction. Use the diagram when installing the new belt.

Locate the automatic belt tensioner on the front of the engine. The tensioner is located on the upper right hand side of the crankshaft. Use the pulley attached to the tensioner to relieve the tension on the belt.

Rotate the tensioner pulley counter-clockwise with the breaker bar and a metric socket. Once the tension is off of the belt, slide the belt out from under the tensioner pulley.

Slowly let the tensioner come back until it stops. Then, route the belt around each fan blade and out of the engine area.

Route the new belt around each fan blade and onto the crankshaft pulley. Follow the routing diagram for the routing instructions for the other accessory pulleys. Once the belt is around all of the accessory pulleys, rotate the tensioner gain with the breaker bar and socket.

Slide the belt under the tensioner pulley and release the tensioner. The tensioner will tighten the new belt as it retracts. Remove the breaker bar and socket from the tensioner and out of the engine compartment. Inspect the new belt to ensure that it is properly seated inside all of the pulleys.

Crank the engine and allow it to run for about 15 seconds. Then, turn the engine off and inspect the belt again just to ensure that the belt has stayed seated inside the pulleys with the engine running. Close the hood.

Tips & Warnings

If the belt routing diagram has faded away, use a pen and piece of paper to draw out the routing direction of the old belt.

Always remove the keys from the vehicle when working inside the engine compartment. This will prevent accidental cranking.

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