Just had the master cylinder replaced and the brakes seem stiff. Also when I'm at a stop I can keep pushing the pedal until it hits the floor. :?

Unfortunately, you have a leak somewhere. The stiffness: You mean the brakes engage earlier now? That'* actually good.

The bleeding isn't good. See if you can find a leaking line. If not...someone else pipe in here. :P

Oh fun for you! I just went rounds with my brakes.

It does sound like either a leak or air in your lines. Did the pedal go to the floor prior to the Master cylinder replacement? If not, it may either be a leaking fitting on the MC or you may need to bleed your brakes again. If yes, you may still have a leak elsewhere. Check all lines, fittings, calipers, and rear wheel cylinders (very common leak). It helps to have someone press on the pedal while you inspect, you might actually see the fluid escaping if it is severe enough. In any event, if your having a braking problem, please address it quickly. Failure to stop leads to bad things. I just noticed my rears brake lines are going to need some attention soon, added to the list.

Thanks, I'll put it on the hoist this Saturday in my class. And I think the inside the old master cylinder were bad... making it not push the fluid causing it to stop.

you may have to do a compleat bleed job.

Who did the master cylinder replacement? Take the car back & have them resolve the problem. It sounds like the brake system is air bound. Have them do a pressure bleed on the brake system. Just my .02.

Is the fluid level dropping quickly in your master cylinder reservoir? If it is, you have a leak somewhere. If the fluid level is not dropping, consider the following: If the pedal is soft or spongy and easily goes to the floor or nearly to the floor, that is usually air trapped in the system -bleed the brakes. When the pedal has a firm initial feel (as you stated) and the car stops normally, but the pedal slowly sinks to the floor under steady pressure of your foot, and no fluid is leaking from the system, the master cylinder is bad. If you release the pedal and press it again, does the pedal come up only to slowly return to the floor under pressure? If so, you have a bad master cylinder.

[edit: a new master cylinder needs to be bench-bled before it is installed in the car. Instructions and special fittings and hoses are provided with new and rebuilt cylinders. ]