Brake Master Cylinder problems of the 2010 Chevrolet Camaro

I purchase the car in 2/2010 & in 5/2010 the brakes started making noise & were loose to the point I had to pump them. I contacted gm took my car to bennett Chevrolet who said nothing was wrong & that's the way they sound, so I took the car to garber the guy drove my car at first said he didn't hear anything, because the noise was obvious ,he then said it was coming from another car. In 12/10 the breaks went to the floor ,only after telling Chevrolet that they will be held responsible. I took the car back to bennett they had to order the master cylinder I got my car back 1/2011. In 7/2013 the same noise again I don't drive the car much so I'm thinking a brake pad even after I notice the exterior around the air conditioner, shifting gears and where the brake fluid goes in looked melt. On 8/2013 I took the car to bennett to be told again nothing is wrong and told the same lie that's the way they sound. 9/2013 went to garber at first they said my brake pads are like new, I told them about the brake problem I had & it's the master cylinder again they repaired it, but I don't know the noise is still there and if history repeats its self the brakes will go to the floor again.