I've been searching and been stuck for a few weeks. Issue still persist.

Replaced

Booster/master
Front brake lines
Tried well working calipers/brakes/disc
Adjust rod out/in with same results
Bled in sequence

​I don't ​​​​believe the prop valve is the issue.

​​​​​-i can hear air when i remove the booster check valve which i dont remember with my other cars.

 

What method are you using to bleed the brakes?

 

If it's one wheel it could be a bad hose.

If all 4 wheels start to drag after driving a while, after working on master cylinder or booster, that is usually because the master cylinder piston isn't returning to the fully out position. Check the linkage inside the car and make sure the booster side comes fully back, adjust the push rod and/or brake light switch. Then you may also need to shorten the push rod on the cylinder side of the booster. Setting it tighter (longer) is not going to help this issue.

The booster is designed to hold a vacuum behind the check valve until the pedal is pressed. If it is good and airtight it can last for days.

Another thing that can cause the brakes to lock up is having the rubber parts ruined by the use of improper fluid. This generally requires the whole system except the metal hard lines to be replaced.

 

Thanks for the response. This is 2 front caliper locking. By tighting the rod, i barely get brakes and by loosing it, it locks up faster. One obvious thing i didnt try is replacing the check valve.