Wierd brake problem

[CCR]

I have a brake problem that is driving me nuts   

Both front and rear brakes are locking after driving round the block a couple of times (the car is not registered here in Sweden and not insured therefore just around the block) and I mean locking not just dragging. I can barely get the car back in the garage with a 505 under the hood 

I have just finished restoring the car and almost everything is new, it has Bendix disc brakes front and drums rear.
Front calipers are restored, rear has new brake cylinders, mastercylinder rebuilt, all hoses new, distribution block and prop valve new.......
Spent so much time bleeding the damn thing I think I can say no air in the system 

I've tried loosening the entire master cylinder and that does not release the pressure, also tried to increase the play between servo and master cylinder.
If I loosen the lines to front or rear circuit on master cylinder pressure release.
Today it worked fine about 15 min of driving, then I stopped to check trans fluid level. After that brakes were starting to lock up, Now I begin to believe it is due to heat 

Any ideas???

[DeltaV]

What type of brake fluid are you using? What are the fluid specifications listed on the brake fluid container?

[CCR]

Brake fluid is regular DOT4+

Forgot to tell that brakes release after 10-15 min with hood open.

[myk]

Based on my Google-Fu skills I've seen that it can be collapsed brake hoses, and/or bad calpers...

[Hard Charger]

the hydraulic pressure in not releasing when you take your foot off the brake.

master cylinder or one of the distribution blocks may be wrong for your set up.

[birdsandbees]

Next time it happens... see if you can pull the brake pedal up a bit after braking.

My 'Bee is that way and needs to be addressed, but I got in the habit a long long time ago of lifting the brake pedal with my toe after each stop.

[pandamarie]

Your brake rod adjustment is to long not letting the Pistons inside the master cylinder go back far enough to release the pressure, I have had it happen on a couple of cars.
If you want to test it, take it out until the brakes are locking up/ or tight then loosen up the bolts on your MC a little at a time until it releases the pressure.
I leave my car in neutral engine off and back the nuts offa little then see if I can push it and keep going until I can push it, doesn't take but a turn or two.
Problem is you need to pull the MC off to adjust the MC push rod.