I have a 92 eg si. And the other day my brakes all the sudeen got a lot of pressure built in them to the point where i couldn't drive so then i had to bleed the brakes to let the pressure out. then yesterday it did it again ...WTF...any help would be great...

basically i need to know how pressure is being built in the lines. BARE in mind i have new calipers rotors and brakes..thats all fine, plus i bled the system and there is not air in there.