How to Replace a Water Pump in a Mercedesby Carl PruitUpdated November 07, 2017
Items you will need
Open end wrench
Socket wrench set
The water pump in your Mercedes Benz is the central part of your engine's cooling system. The Mercedes water pump is designed on a centrifugal pump that is operated by the engine's crankshaft and driven by a belt. The inlet valve on the top of the water pump allows the coolant to be generated from the radiator, back through the water pumps impellers and back out into the engine. The design is very simple, allowing for easy removal and installation. Replacing the water pump in your Mercedes should only take you a couple hours to complete.
Take the cap off of the Mercedes radiator and also off the coolant overflow reservoir. Place a drain pan underneath the drain plug of the radiator located on the bottom of the radiator.
Open the drain plug with an open end wrench and allow the coolant to drain until the radiator is completely empty. Once it is drained, close the drain plug.
Detach the hose at the top of the water pump that runs to the radiator by undoing the hose clamp with a screwdriver.
Undo the negative battery cable from the battery post with an open end wrench and place the cable out of the way, taking care not to touch any metal parts with the end of the cable.
Unplug the electrical connector that is attached to the fan blade and unbolt the fan blade from the front of the water pump with an open end wrench. Remove the fan blade from the engine compartment.
Remove the fan belt by using a socket wrench to loosen the pulley that is holding the belt on. Detach the water pump from the engine by using a socket wrench to take off the bolts. Once the bolts are out, use a screwdriver as a pry tool to dislodge the water pump from the engine block.
Scrape the face of the engine block where the water pump is attached with a putty knife to remove any remaining gasket material or debris. Use a piece of emery cloth to finish cleaning the surface of the engine block and prepare it for the new water pump.
Spread a layer of gasket seal around the face of the new water pump and lay the cardboard material gasket that is provided with the new pump over the face of the water pump. Attach the water pump to the engine block and secure it with bolts.
Reattach the belt around the fan pulley and tighten the belt by pulling back on the pulley as you tighten the bolts that hold it onto the engine. Place the fan blades back on the front of the water pump and attach the blades with bolts.
Put the radiator hose back on the top of the Mercedes water pump inlet valve and attach with a screw clamp.
Secure the negative battery cable to the battery and then fill the coolant overflow reservoir half full with coolant and place the cap back on the reservoir.
Fill the radiator with coolant and water and put the cap back on the radiator.
Remove the drain pan from underneath the radiator drain plug and dispose of the drained coolant at your local recycling center or automotive supply center. Start the motor to allow the water to begin cycling through the water pump. Then verify that there are no leaks around the water pump. When you are satisfied, turn the motor off.
Allow the engine to cool down before attempting to do any mechanical work on it.