Despite having incredible engineering, one weak spot of BMWs--particularly on the Z3 and E36 3 Series--is the cooling system. The thermostats and water pumps on these models are known to suffer from failure frequently, in which case they need to be replaced before damage is caused to the engine. When the water pump fails, there is no way to make repairs; it must be replaced with a new one.
- Skill level:
- Moderately Challenging
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Things you need
- Floor jack
- 2 jack stands
- Socket set and ratchet
- Flathead screwdriver
- Container for coolant
- New water pump
- New water pump O-ring
- White lithium grease
- BMW fan removal tool
- Wire brush
Drain the coolant. To do this raise your Z3 with a jack and lower it onto jack stands. Place the heater control knobs to the hottest setting. Turn the ignition on but do not start the engine. Turn the passenger compartment fans to their lowest setting.
Remove the drain plug for the coolant from the engine block, which is located just under the manifold. Place a container to catch the coolant. Replace the plug when all of the coolant has been drained out. Remove the plastic drain plug from the bottom of the radiator and drain the coolant into the container. Replace the plug and tighten it to only 2 to 3 pound-feet of torque.
Pry off the small plastic caps that covers the belt tensioner. Rotate the tensioner to release the tension on the belt. Slide the belt off of the pulleys. Remove the fan by placing the special fan removal tool (available from BMW parts suppliers) on the fan to hold it still while you remove the fan bolt by turning it clockwise (it is reverse-threaded) with a 32mm wrench.
Remove the four small nuts that hold the fan pulley to the water pump. Loosen and remove the four nuts that hold the water pump to the engine block. Tap the water pump with a rubber mallet to free it from the engine block and then remove it from the engine bay.
Clean the holes in the engine block where the pump mounts so there is no debris or corrosion. Use a rag and wire brush. Install a new water pump O-ring. Place a small amount of white lithium grease around the O-ring to promote a strong seal.
Install the new water pump and tighten the bolts that hold it to the block to 8 pound-feet with a torque wrench. Reinstall the fan pulley, the fan and all of the belts in the reverse of removal. This is also a good time to install a new thermostat for extra insurance. Top off the coolant.
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