WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
The following illustration 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.