Brakes failure

The brakes on my fathers 95 Crown Vic (Police Interceptor), doesn't work too well.

If I press the breaks, and sitting at a red light, the brake will just "drop" to the floor slowly, and release brake pressure, causing the car to roll.

Also, if I press the brakes, let go a little, and press again, it goes right down to the floor instantly.

Pressing the brakes hard and fast also cause it to go to the floor, but make the power booster "area" make a whine sound.

My father can't tell if it's the master cylinder or the power booster.

Any ideas?

The Diafram (rubber gasket) is broken in the power brake booster.Replace the booster and your problems will be fixed

If the pedal falls to the floor, it is the master cylinder by-passing internally. Replace the master cylinder. If it were the booster, the brake pedal would be really hard to push.

I agree with way2old on this one.

If the pedal falls to the floor, it is the master cylinder by-passing internally. Replace the master cylinder. If it were the booster, the brake pedal would be really hard to push.