1996 Ford Windstar brakes

POWER BRAKE FUNCTION TEST
With engine stopped, remove vacuum in system by pumping brake pedal several times. Push pedal down as far as it will go. If pedal moves downward slowly, hydraulic system is leaking. Check hydraulic system for leaks.
With pedal pushed down as far as it will go, start engine. If pedal moves downward, vacuum system is okay. If pedal does not change position, a problem exists in vacuum system. Check vacuum system for leaks
BRAKE PEDAL RESERVE
If complaint is low or bottoming out brake pedal, run engine at idle with transmission in Park or Neutral. Lightly depress brake pedal 3 or 4 times. Wait 15 seconds for vacuum to build in booster. Depress brake pedal until it stops moving downward.
While holding pedal down, raise engine speed to about 2000 RPM. Release accelerator pedal. Brake pedal should move downward as engine speed returns to idle. If results are correct, system has proper pedal reserve. If results are not correct, check for adequate vacuum. If vacuum is okay, replace vacuum booster.