front brakes are locking up after a few miles. what could it be? on 2005 Chevrolet Colorado

we have replaced brake booster, master cylinder and all also has been bled.

Really hard to say without looking at the vehicle in person, but one thing that usually causes that is contaminated brake fluid. If somebody put anything other than DOT 3 or DOT 4 brake fluid in your master cylinder, the fluid can become contaminated and cause the rubber seals to swell up.