How to Change a BMW Water Pump


The cooling systems on BMW engines have had a history of problems for a while, primarily with the water pump and thermostat. Over time, the plastic impellers that were used in the BMW water pumps would become brittle from use and begin to break away, causing the engines to overheat and creating other problems. The plastic impellers have since been changed to metal impellers on the newer water pumps. You can replace the water pump on your BMW in about three or four hours, saving you the cost of having someone else replace it.

Things You'll Need

  • Open-end wrench
  • Crescent wrench
  • Drain pan
  • Standard screwdriver
  • Socket wrench set
  • Rubber mallet
  • Wire brush
  • White lithium grease
  • Coolant
  • Detach the negative battery cable from the battery of your BMW with an open-end wrench and crescent wrench. Move the cable out of the way so that it does not come into contact with any metal parts.

  • Remove the radiator cap and the cap on the coolant overflow tank located on the passenger side of the BMW engine compartment. Locate the drain valve at the bottom of the radiator and place a drain pan just below it.

  • Open the drain valve with an open-end wrench and allow all the coolant to drain into the pan. When it is completely drained, locate the coolant drain plug on the engine block, just under the manifold on the passenger side of the engine.

  • Move the drain pan underneath the coolant drain plug of the engine block and open the plug with an open-end wrench. Allow the coolant to drain out and then close both the engine block drain plug and the radiator drain plug.

  • Find the main drive belt that winds around the pulley on the fan and locate the tensioner cap on the front of the center pulley. Use a standard screwdriver to remove the cap from the tensioner pulley.

  • Loosen the bolt on the tensioner pulley with a socket wrench to release the pressure on the main belt. Note how the belt is looped around the pulleys so you can put it back properly and then remove the belt from the pulleys.

  • Locate the bolts on the back of the fan blade and remove the bolts with an open-end wrench. Once the fan blade is loose, remove it from the engine compartment.

  • Remove the fan pulley from the front of the water pump by unbolting the four bolts that attach the units with a socket wrench. Detach the four nuts that are holding the water pump to the engine block with a socket wrench.

  • Tap the water pump with a rubber mallet to loosen the seal and pull it away from the engine. Clean any debris away from the engine block where the water pump was attached with a wire brush.

  • Place a layer of white lithium grease around the O-ring that was included with the new water pump. Position the new water pump and O-ring over the engine block and attach the pump using a socket wrench to secure the pump with nuts.

  • Reattach the fan pulley to the front of the water pump, securing the bolts with a socket wrench. Connect the fan blade to the front of the fan pulley with bolts and check all connections to verify they are secure.

  • Place the fan belt around the pulleys the same way it came off and then tighten the tensioner pulley with a socket wrench. Put the tensioner pulley cap back over the top of the pulley.

  • Fill the coolant overflow reservoir half-full of coolant and replace the cap, then fill the radiator with coolant. Place the cap back on top of the radiator and remove the drain pan from underneath the vehicle.

  • Reattach the negative battery cable to the BMW battery and start the engine to verify the water pump is working properly. When you are satisfied, turn the engine off and dispose of the drained coolant at your local recycling center or automotive supply.

Tips & Warnings

  • To avoid injury, never open the radiator cap while the engine is still hot.

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