BMW engine cooling systems have had a long history of problems, mainly with the water pump and thermostat. Over time, the plastic impellers used in BMW water pumps became brittle from use and began to break down, causing the engines to overheat and other problems. Since then, the plastic impellers were replaced with metal impellers in the new pumps. You can replace your BMW’s water pump in about three to four hours, saving you the cost of having someone else do it for you.
Unhook the negative battery cable from your BMW’s battery with an open end wrench and a wrench. Move the cable out of the way so it doesn’t come in contact with metal parts.
Remove the radiator cap and coolant surge tank cap located on the passenger side of the BMW’s engine compartment. Locate the drain valve at the bottom of the radiator and place a drain pan underneath.
Open the drain valve with an open wrench and allow the coolant to drain into the pot. When the drain is complete, locate the coolant drain plug on the engine block, just below the handle on the passenger side of the engine.
Move the drain pot under the coolant drain plug on the engine block and open the plug with an open wrench. Allow the coolant to drain out and then close the engine block cap and radiator cap.
Find the main drive belt that surrounds the pulley on the fan and locate the tensioner cover in front of the center pulley. Use a standard screwdriver to remove the tensioner pulley cover.
Loosen the tensioner pulley bolt with a socket wrench to release the pressure on the main belt. Watch the belt wrap around the pulleys for proper positioning 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 blade is loose, remove it from the engine compartment.
Remove the fan pulley from the front of the water pump by removing the bolts that join the units together with a socket wrench. Unhook the four bolts holding the water pump onto the engine block with a socket wrench.
Tap the water pump with a rubber mallet to loosen the seal and remove it from the engine. Clean any debris from the engine block where the water pump was attached with a wire brush.
Place a coat of white lithium grease around the O-ring included with the new water pump. Position the new pump and O-ring over the engine block and attach the pump using a socket wrench to secure the pump with bolts.
Reattach the fan pulley to the front of the water pump, securing the bolts to the front of the water pump, and the bolts with a socket wrench. Attach the fan blade to the front of the fan with bolts and check the connections to see if they are secure.
Place the fan belt around the pulleys the same way you removed it and tighten the tensioner pulley with a socket wrench. Place the tensioner cover back over the pulley.
Fill the coolant overflow reservoir half full of coolant and replace the cap, then fill the radiator with coolant. Replace the cap on the radiator and remove the drain pan from under the vehicle.
Reconnect the negative battery cable to the BMW and start the engine to verify that the water pump is working properly. When you are satisfied, shut off the engine and dispose of the drained coolant at your local recycling or automotive parts center.
Warnings
To avoid injury, do not open the radiator cap while the engine is hot.