It is terrible when driving. The pedal goes to the floor and provides minimal braking force. It's scary actually! Last time I went out and checked it, and it was about 7fahrenheit. I live in MN. I can pump up the pedal to get a firm pedal pressure, but as soon as you start the car, the pedal goes to the floor and if you pump the pedal when the engine is running, you can get to a point where the pedal stiffens up a little, but it does not stay there, and at times the pedal goes straight to the floor. One time when I did this, the ABS light came on. This seems like it's a master cylinder issue. Might have fluid past the first seal.