Master Cylinder: Notes
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2003 Ford Pickup. 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 and must be rebuilt or replaced.