Pump-Out Valves
WARNING: This page is about a different car, the 2010 Volvo V70, 2009 Volvo V70, and 2008 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.
The pump-out valves are used to balance the pressure in the passenger compartment.
The pump-out valves are equipped with rubber flaps. The flaps open when the air pressure is slightly higher in the passenger compartment than outside. When the air pressure is as high on the inside is outside the flaps are closed. This prevents water from entering.
On 4-door vehicles the air outlets are located in the edge between the rear shelf and the rear window. The air goes from here through the cargo compartment and out through the pump-out valves behind the rear bumper.
In 5-door vehicles, the air passes directly out through the air vents in the cargo compartment.