In this guide, you will learn how to manually rotate (turn over) the crankshaft on Mercedes-Benz engines. This is often necessary if your Mercedes does not start and you want to verify that the engine is not seized or locked up. This procedure is also required for a number of maintenance procedures including for changing the timing chain, check for timing chain wear, time injection pump, camshaft replacement etc.
How to turn Mercedes engine by hand
The procedure for turning Mercedes engine by hand is very simple. You will place the 27mm socket at the bolt located at the center of the crankshaft, attach the ratchet wrench to manually turn over the engine.
To manually crank a Mercedes-Benz engine you will need:
Park your Mercedes-Benz and set the parking brakes.
Allow the engine to cool down.
Pull the hood release under the hood.
Open the hood and locate the crankshaft pulley at the front of the engine.
Place the 27mm socket on the bolt at the center of the crankshaft.
Rotate the ratchet clockwise. Do not rotate the engine counter clockwise.
You will need to apply a considerable amount of force. V8 and V6 engines are harder to turn over than V6 and 4 cylinder engines. Also note that as the various cylinders reach the Top Dead Center (TDC), turning the crankshaft will get harder then easier once past the TDC. If you are having a hard time turning over the engine, remove the drive / serpentine belt and try again. If it is still difficult to manually crank your Mercedes-Benz engine, remove the spark plugs. If your crankshaft won't turn, then you most likely have a mechanical problem.
Common Reasons Engine Won't Turn Over
If your engine will not turn over, in most cases it is due to mechanic problems. Typical problems that can prevent a car from turning over include.