While driving about 10 to 15 miles the rear brakes apply w/o pedal application. I replaced the shoes drums hardware wheel cylinders. while the rear brakes are locked up
the brake pedal is hard as a rock engine running or not.
still does the same thing. I don't know if it is the master cylinder or Hydro boost. I would be thankful for any help.

If you have any suggestions please. I have been a mechanic for over 40 years and never seen this happen.

thanks again