C15A brakes jamming

[Dave Mills]

Have you by chance overhauled your master cylinder? Maybe just maybe if you have you could have placed the fluid return washer in back the front, upside down, etc. The washer is usually a wave washer, If this little washer is in back the front it will allow the fluid out into the wheel cylinders and will not allow it to return to the reservoir tank, keeping the brakes engaged. When you say you have released the pressure is this from all 4 wheel cylinders or from the master cylinder? Just a thought as I have suffered the same problem with my own repairs, not a C15A but never the less have suffered the same problem.