Check Valve Test
WARNING: This page is about a different car, the 2001 Acura Integra. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect power brake unit vacuum hose at booster. Start and idle engine. Check for vacuum at booster end of hose. If vacuum is not available, vacuum source or check valve is faulty. Repair vacuum source or replace check valve, and retest.