Checking for leaks:

WARNING: This page is about a different car, the 2008 BMW X5 and 2007 BMW X5. 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 Tie Rod Arm And Tie Rod Joint

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Identifying Power Steering Components

Courtesy of BMW OF NORTH AMERICA, INC.

Check all visible connections, hoses, lines and steering gear for traces of fluid.