In recent years, an electric water pump has become the go-to for modern cooling systems. Using an electric water pump over a belt-driven pump has allowed BMW's engineers to simplify engine maintenance and cut costs. Less time spent in the shop means more money and more time on the road for the owner.
The electric pump also introduced a self bleeding procedure to the vehicle, turning the tedious task of bleeding the system into one you won't ever have to think about. Bleeding the cooling system on previous generations of BMW proved to be tricky at best. It was common to get air pockets stuck inside the engines, leading to cooling issues. However, the self- bleeding procedure introduced on the F30 chassis eliminates any trouble you may have bleeding the system.
Steps to bleed a BMW cooling system
Any time you drain the cooling system, or it's opened anywhere other than the expansion tank, you should bleed the system. Bleeding the system will ensure that no air pockets exist and the coolant can do its job properly. Because it's an electric pump, a strong battery is necessary for the bleeding process. The BMW service manual recommends that a battery charger be hooked up during the process, though we completed it without one.
To initiate the self bleeding procedure:
Have the key with you and get into the driver's seat.
Press the start button once to put the ignition into accessory mode.
Set the heater to max temp and the fans to their lowest setting.
After that, depress the accelerator pedal for about ten seconds to start the bleeding. You'll know the process has begun when you hear the coolant moving inside the engine and radiator. Once the process has started, leave the car be for 8-10 minutes. After that, the process will be complete, and you'll be ready to drive with a fully bled cooling system.