My cavalier has air in the brake lines. It happened all of a sudden when i went to drive it today.. Had good brake pressure.. then the brake pedal just caved in and i had hardly any brakes.

I checked and found that i have lots of air in my system all of a sudden. I looks at all the lines running from the master and they look fine and were tight. all 4 rubber hoses were dry and not leaking any fluid. The master is still holding brake fluid..

What could it be?

Oh and for those who helped me the Camaro brakes, Thanks, I got them done and they are fine... Just as soon as i finished the camaros, i went to move the cav out of the way and the cavs brakes went. The calipers, drums, and brake lines are pretty new also.

 

If the pedal goes to the floor and you have no external leaks, it is likely the master cylinder leaking internally.
The booster merely provides assist to make it easier to push the pedal in. About the only thing that could happen to the booster is that the diaphragm would have a leak and that would cause you to have to use more brake pedal pressure.