"Clean and Adjust", Master Cylinder Replacement

These so called mechanics test drove my fiance's car when we spoke with them about her brakes working fine in most cases, but other times the pedal would be all the way against the floor of the car but it would keep rolling. The emergency brake also failed on inclines. They determined that all she needed done was a "clean and adjust" of her rear brakes, which after some research, is a useless procedure designed only to generate profit for the store, but is usually accompanied by an inspection to determine if there are other issues with the brakes. While they did list a few other repairs that would need done in time, none of them had to do with the issue at hand. The next day, my fiancé was driving home from work and was entirely unable to stop with either the normal or emergency brakes. By some miracle, she made it home alive and the car was intact, but now KM auto repair of Kennesaw, GA, is charging us 319 dollars for a new master cylinder. A trained mechanic would have known the symptoms of a failing master cylinder and would have noticed it from the description of the problem, the test drive, and from inspecting the brakes during the "clean and adjust". My fiance could have died because of their ineptitude. Remember that whoever works on your car holds your life, livelihood, and that of your loved ones in their hands. Take your business and your money to a real mechanic that will actually take care of you and your car.