What is wrong with a 92 Accord if you have to pushed the pedal almost to the ground to get the brakes to work when the brake lines and cylinders have no leaks and you have replaced the master cylinder?

If it has rear brake shoes instead of disc pads, then they need adjusting. Also make sure you have bleed the brake system to remove the air that got into the system when you changed the master cylinder. Bleed starting at the Right Rear and then LR, RF, LF. the bleeding sequence is wrong. It goes front left, rear right, front right, rear left. Check me on that, though. I know you can't just do one end of the car then the other. You are INCORRECT. The bleeding sequence listed in my answer is CORRECT. You bleed the farthest wheel from the master cylinder first, then the next farthest, etc. That is RR, LR, RF, LF. You can indeed bleed both rear wheels first and should. I think you need to check this out. Look on any reputable site you wish and you will find that I am correct. Her is one site: http://autorepair.about.com/od/brakerelateddiyjobs/l/aa091804f.htm