You may have lost fluid from a bad master cylinder, your pads being too low, or a leak in one of the brake lines. the reason why your pedal is traveling all the way down is because there is air in your brake system. the air will not let the system build enough pressure to properly apply the brakes.
reason being: the fluid cannot be compressed and air can be compressed. with an air free system the fluid will build pressure and put force to whatever it is being applied to. in this case the calipers to brake pads to rotors. when there is air present in the system the air will compress, causing you to lose pressure, and brake performance.
i recommend bleeding the flushing/bleeding the brake system, finding and fixing the leak. if you dont find the leak then you will run into this problem more frequently...
Adam
reason being: the fluid cannot be compressed and air can be compressed. with an air free system the fluid will build pressure and put force to whatever it is being applied to. in this case the calipers to brake pads to rotors. when there is air present in the system the air will compress, causing you to lose pressure, and brake performance.
i recommend bleeding the flushing/bleeding the brake system, finding and fixing the leak. if you dont find the leak then you will run into this problem more frequently...
Adam