I have new symptoms...when I'm driving, there is a whoop whoop noise coming from the front left brake. When I press the brake pedal the sound goes away but the master cylinder makes a very loud metal on metal screeching noise for the first 1 inch of pedal travel. If I don't push the brake pedal, the whoop whoop noise gets louder and louder until it is a steady rubbing noise. I have changed the calipers and pads and this noise started right after i had them changed...could it be my brake booster? I am really concerned about the noise coming from the master cylinder area.