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.
Press in lock (1) before installing fast-release coupling.
Push on hose.
Quick-connect coupling must clearly snap audibly into place.