while driving my 66 t-bird the rear brakes will automatically engage. once i release the pressure by loosing a bolt on the master cylinder the brakes release. i have changed the master cylinder, wheel cylinders, shoes, pads, power booster, and proportional valve and i still have the same problem. can anyone help?

reggie

When you installed master cyl & booster did you adjust thepush rod length? In my 61 the lgth. is.962 to .967. DAN

The 66 uses a power booster rod length of 0.990 to 0.995 inch measured end of rod to brake booster housing surface. This housing surface is between the studs that the master cyclinder normally bolts to. You can make a gage from a 2-7/8" by 1-3/4" piece of stiff single ply cardboard. Measure over 1-1/16" from one side of the 2-7/8 edge and cut out with a razor a 3/4" wide section that is 0.995" (measure with a dial indicator or even a micrometer) long.
Your rear brake hose may be acting like a check valve.
Pensacola, FL