WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Oil Pipes
Courtesy of VOLVO CARS OF NORTH AMERICA.
Install lower pipe. Use a new O-ring.
Install the upper pipe (return line) with its mounting in the control system cover.
Install connector loosely. The pipe cap nut is tightened later.