I come to a stop at light but then I feel the pedal go down so I push down hard. Feels spongy.Had them checked cause of squeal but dealer said just dust in them.Now yesterday had to brake on left turn lane cause lady pulled out in frt of me from Frys (And me pulling in)head on you can bet I stood on the brake pedal! and it stopped fast.So what can it be causing this ? Now mind its not every stop. Thanks