Cooling System Bleeding
WARNING: This page is about a different car, the 2003 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Open vent plug on coolant expansion tank. Turn ignition on. Place heater control in maximum temperature position. Set blower motor to low setting to start auxiliary water pump. Fill expansion tank with coolant until no bubbles appear at vent plug. Close vent plug. Fill coolant until it reaches maximum cold fill level. Start and run engine and continue to add coolant to expansion tank as coolant level drops, until coolant is free of air bubbles. Check for leaks.