2. Blow air into the vacuum hose using your mouth from the vacuum pump side and verify that the air flows to the intake manifold side, then blow air from the intake manifold side and verify that the air does not flow to the vacuum pump side.
If there is any malfunction in the check valve, replace it with the vacuum hose as a single unit..
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Test yourself
A quick Mazda 3 quiz: every answer comes with an explanation and a link to the manual page.
