Between intake manifold and vacuum pump
WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.
- Remove the vacuum hose. (See VACUUM HOSE REMOVAL/INSTALLATION (VIN L) (US) .)
- Blow air into the vacuum hose from the vacuum pump side using your mouth 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 of the inner check valve, replace it together with the vacuum hose as a single unit.