Bypass Condition Test
WARNING: This page is about a different car, the 2004 Ford Ranger, 2003 Ford Ranger, and 2002 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.
To check master cylinder for internal leak, disconnect brake lines at master cylinder. Plug outlet ports of master cylinder. Apply brakes. If pedal height cannot be maintained, master cylinder has internal leak (bypass) and must be rebuilt or replaced.