what would be casing my 99 grand am to have no pressure in the brakes? I just got my master cylinder replaced about a year ago. i have also checked for leaks and have found nothing apparent. i did remove my master cylinder to see if there was fluid behind it and there was none. could it be something internally wrong with the cylinder or something else? please help asap.

Check the vacuum to the booster.

What do you mean when you say "no pressure"... Is your pedal high and hard or very low and spongy/unresponsive? High and hard would be a failure in the vacuum power booster as mentioned above. A low, spongy pedal indicates a pressure loss somewhere in the system. Check the fluid level in the master cylinder reservoir. Then with a flashlight, trace the brake lines from the master cylinder down to all four wheels and back along the frame, looking for wet and/or rusted-out sections. If everything looks fine, pull the rear wheels and remove the brake drums and inspect the condition of everything inside. To lose pedal, it would have to be something drastic....but if you had a moderate to badly leaking wheel cylinder, you'd never see it behind the wheel and it would suck your reservoir dry til it pulled air, which would make the rest of your pedal vanish,

Also, if your new master cylinder *did* fail, it would be bypassing which would typically give you fair stopping power when you first applied the pedal but it would immediately begin to fade to the floor unless you pumped it for as long as you were applying it.

II have checked the booster and it is fine. I pulled the vac hose out and it let out a considerable amount of pressure. The pedal sits where it should it jus barely takes any force to push it down when the car runs. When its off it is still pretty easy to press down. How can I test the master cylinder to see if its the problem?