2007 Mitsubishi Grandis • 2.4L 4 cylinder Automatic • 75,000 miles

Good day! I noticed that every time I had to brake hard and depress the brake pedal suddenly and deeply, I hear a metallic grinding sound, after which a swooshing, whistling sound can be heard when I release the brake. The swooshing sound goes on but disappears later, especially after I pump the brake pedal up and down. It has been like this since I bought the car. I described the noise to the Mitsubishi service center but they did not address it and no one can explain to me what it is. I saw a post here that seems to describing the same thing in his Grandis (same year), but have yet to come across another model that describes what I just wrote here. If this is normal for this make, is there anyway to minimize that swooshing sound? I forgot to mention that I have to apply the brakes deeper after braking hard wen I have to make stops. It goes back to normal eventually though.
March 9, 2014.

Have your brakes checked for wear and have the vacuum booster checked it may be leaking causing the swooshing sound.

Mar 9, 2014.