Check Valve, Checking, RS 5
WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2016 Audi S4, 2016 Audi A4 Quattro, 2016 Audi A4, 2015 Audi S4, and 2015 Audi A4 Quattro. However, it is still accessible from the selected car via links, so may be relevant.
Valve must allow air to flow in direction of arrow.
Valve must remain closed in opposite direction.
Observe correct installation position.
the arrow points to the vacuum pump.