One Way Check Valve Check
WARNING: This page is about a different car, the 2000 Mazda Protege, 2000 Mazda Millenia, 2000 Mazda MX-5 Miata, 2000 Mazda MPV, and 2000 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.
Remove one way check valve. Blow in valve into direction of arrow. Air should flow. Blow into valve in opposite direction. Air should not flow. If flow is not as specified, replace valve.