WARNING: This page is about a different car, the 2005 BMW 745i, 2004 BMW 745i, 2003 BMW 745i, and 2002 BMW 745i. However, it is still accessible from the selected car via links, so may be relevant.
The following illustrations shows the arrangement of the power steering components and lines.
Fig 1: Identifying Power Steering Components And Lines
Courtesy of BMW OF NORTH AMERICA, INC.
Check all visible connections, hoses, lines and steering gear for traces of fluid.