I did little research on calipers locking up. ive replaced the calipers and brake booster. im leaning more toward the master cylinder but ant tell if it leaks or not. anybody now anything else I could try to see if it helps.

 

I've seen old disc brake vw's lock up the calipers, because the inside of the brake hose was swollen up... incoming pressure from the master cylinder would overcome the restriction in the hose, but when you let off of the brake pedal, the hose restriction prevented the fluid from coming back up out of the caliper.

the pressure would bleed off pretty quickly... the hose looked fine from the outside.

 

That is exactly what I was going to say, except it was a 2000's Hyundai Replace your rubber lines as they can act like a check valve when they wear out.

 

do I need to replace front and back brake line

 

do you actually have disc brakes on the back? i would start with the axle that's locking up.

if it is a hose problem, it might be a good idea to change all of the rubber brake hoses, even if you don't have discs on the back axle.