Only when filling!

WARNING: This page is about a different car, the 2010 BMW M6, 2009 BMW M6, 2008 BMW M6, 2007 BMW M6, and 2006 BMW M6. However, it is still accessible from the selected car via links, so may be relevant.

Perform filling operation slowly.
Set heater to maximum temperature and turn fan down to lowest speed.
Start engine and run at idle speed.
Fill coolant expansion tank with 250 ml above max. (250 ml correspond to A=18 mm).
Run engine for 15 mins.
Cooling system vents itself.
Coolant level must drop to marking.
If necessary, correct coolant level.
Close cap on expansion tank.

Fig 1: Identifying Coolant Expansion Tank Dimension

Courtesy of BMW OF NORTH AMERICA, INC.

NOTE: If necessary, check COOLING SYSTEM FOR WATER LEAKS .