BMW Z4 cooling system components include:
- Radiator and coolant overflow tank
- Belt driven coolant pump bolted to the front of the engine block.
- Electric cooling fan, DME controlled
- Electric (auxiliary) cooling fan attached to front of radiator - the cooling fan is controlled by the engine control module (ECM) via an output final stage.
- Electrically heated thermostat
- Automatic transmission cooler or heat exchanger (if equipped)
- Heater valve and heater core (for climate control)
- Coolant level sensor inside expansion tank
- Coolant temperature sensor at cylinder head
- Coolant hoses and lines
Engine coolant typically consists of a 50%-50% mix of ethylene glycol and water with various additives (example: water pump lubricant). Hot coolant eventually dissolves various internal engine parts, particularly as it ages and mixes with impurities. The manufacturer therefore recommends that you drain and flush the cooling system approximately every 2 years. Be careful when working with ethylene glycol coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse the area with water.
Draining and filling your cooling system is not only a maintenance requirement but also a prerequisite of many repairs. Engines used in BMW Z4 6-cylinder models hold about 10.5 liters of ethylene glycol: water mix.
In this article, I'll go over the steps involved with replacing the engine coolant on BMW Z4 with an S54 engine. Other models are similar. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the radiator or expansion tank cap.
Do not remove the radiator or expansion tank cap or work on any other part of the cooling system while the engine is hot. Coolant or hot steam may escape and will scald you. To do any work on the cooling system, wait until the engine has cooled off.
To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.
Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.
Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.
Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.
Lift and support the front of the vehicle safely. Remove the engine splash shield. See our tech article on splash shield removal for more info.
|Draining cooling system:|
Working at the top of the coolant reservoir (expansion tank), remove the cap.
The coolant drain is located on the left side of the radiator (red arrow). Working at the lower left side of the radiator, remove the radiator drain plug (green arrow).
Allow the coolant to drain into the bucket (red arrow). Once the coolant has stopped dripping, reinstall the radiator drain plug.
Place an empty three-gallon bucket under the right side of the engine, near the power steering rack. Working at the right side of the engine block near the engine mount bracket, remove the engine block drain (green arrows). The block drain is a 13mm plug, located just below the cylinder two exhaust header. Allow the coolant to drain into the bucket. Once the coolant has stopped dripping, reinstall the block drain plug.
|Filling cooling system:|
Filling cooling system: Remove the expansion tank bleeder screw (red arrow). Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until coolant comes out of the expansion tank bleeder screw and reaches MAX COLD. Fill until the coolant stick reaches MAX COLD (green arrow) on the coolant expansion tank filler neck (inset). Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Working at the top of the expansion tank, loosen the coolant expansion tank bleeder screw. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Slowly fill the expansion tank until the coolant coming out of the expansion tank bleeder screw is free of bubbles. Once the coolant is free of bubbles, tighten the expansion tank bleeder screw. Start and run the engine at idle until it reaches operating temperature. Shut the engine OFF and allow it to cool. Check the coolant level in the expansion tank. Top up the coolant until the level indicator is at MAX. Once at MAX, your cooling system is full. Min and Max levels are embossed on the coolant expansion tank for reference. Install the engine splash shield and check the cooling system for leaks.