WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Dirt Guard & End Of Piston
Courtesy of VOLVO CARS OF NORTH AMERICA.
Blow ducts clean with compressed air.
Coat cylinder lining, piston (2) and new O-ring (4) with brake fluid.
Install lubricated O-ring (4) in groove in cylinder. Install dirt guard in end of piston.