brakes

Hello, I have a1996 pontiac gm. 3.1 v6 The brakes keep locking up. Even with new brakes in the frount and back. They seem ok for awhile then they lock up again not all the time. Now you can hear air insde when appling the peddle. If you need to apply the brakes for a sudden stop they are there.

if the calipers at the wheel cylinders are working, and not frozen or seized, then I'd say your brake booster is malfunctioning.
But you could very well hav other things going on too. You should probley take it to a Certified Mechanic to get it checked out ASAP.

are all 4 corners locking up, or is it just front or rear?