Hard brake pedal

First of all, never ever push the brake pedal to the floor. Doing so runs the rubber lip seals over the crud and corrosion that builds up in those areas where the pistons don't normally travel. You may have a damaged master cylinder now, and the internal leakage often does not show up for two or three days.

Most front-wheel-drive cars use a split-diagonal hydraulic system with the right front and the left rear on the same circuit. On the GM cars, when there is a leak or when the brakes are bled and the pedal is pushed over half-way, there is a valve that trips in the master cylinder to block those two ports. The only way I have ever found to reset the valve is to loosen the cap on the reservoir, open the bleeder screw on one of those wheels, then give it a very short, quick burst of compressed air. Let it gravity-bleed after that. Once the air is bled out, close the bleeder, "irritate" the brake pedal a little by hand, then open the bleeder once more. You don't have to bleed all the wheels when replacing a leaking line.

Just to add a little, if you are trying to bleed the system with ABS, you have to have the proper scan-tool to open the ABS solenoids to bleed the system. I have learned this from another Tech on our forum here. He will always tell you to have a Tech open the solenoids with an ABS scan-tool. Just a thought.