Check Valve Operation Check

WARNING: This page is about a different car, the 2012 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.

Remove the check valve (Refer to MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER ASSEMBLY .
CAUTION: Replace the check valve when it is faulty.

Using a vacuum pump, check operation of the check valve.

VACUUM PUMP REFERENCE CHART

Vacuum pump connection	Normal condition
When connected to the booster side (1)	Vacuum is generated and maintained.
When connected to the engine side (2)	No vacuum is generated.

Fig 1: Checking Operation Of Check Valve Using Vacuum Pump

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.