How to Replace the Timing Chain on a 300Dby James Marshall; Updated November 07, 2017
Items you will need
Socket wrench set
Clamp for camshaft gear
The 300D is a member of the series of executive cars by Mercedes Benz with the internal designation W123. The 300 designation indicates the car has a 3.0-liter engine, and the D designation means the engine uses diesel fuel. The timing chain in the Mercedes Benz 300D is an endless timing chain that contains a single master link, or connecting link. You must use a chain-breaker to separate the master link and remove the timing chain.
Remove the spark plugs with a socket wrench, and disconnect the valve covers.
Clamp the timing chain to the camshaft gear. Plug the opening in the cover for the timing chain with shop rags. Attach a chain-breaker to the master link on the timing chain. Separate the master link by using the chain-breaker. Release the clamp from the camshaft gear, and remove the shop rags from the hole in the timing chain cover.
Attach the master link on the new timing chain to the master link on the old timing chain. Turn the crankshaft clockwise with a socket wrench as you pull the old timing chain through the camshaft sprocket. Maintain tension on the old timing chain, and stop turning when the master link on the old chain is in the 12 o'clock position on the camshaft sprocket.
Disconnect the master link on the old timing chain from the master link on the new timing chain, and remove the old timing chain from the camshaft sprocket. Connect the free end of the master link on the new timing chain with the other free end of the timing chain. Make this connection from the rear of the camshaft sprocket, so that you can see the lock washers on the timing chain.
Turn the crankshaft clockwise to align the timing mark on the crankshaft with the timing mark on the crankcase. This will close the master link on the new timing chain. Turn the crankshaft at least one full turn clockwise to ensure the new timing chain is properly seated.