Brake problem

when I hit the brakes all the way the brake does not release back and the car stays still , I have to park aside and turn the engine off and wait for a while and turn the engine on again or sometimes it releases when I keep on pushing the brake pedal a few times . My mechanic suspects the ABS , but he changed the abs with another recondition abs and the same problem is still there . PLEEEEZ help if a one have any ideas . He checked the car on the vac but he found no error , we check the parking switch and it seems to be ok , we check the wheel sensors and the readings of the 4 wheels are the same !!!! Anybody have any ideas !'