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: Venting Boot
Courtesy of VOLVO CARS OF NORTH AMERICA.
Place the boot in the resting position. Place a small screwdriver between the shaft and the boot to vent it.