When active in the trade I had a couple of cars in with similar problem of the
wheels (4) locking after a short drive. Releasing the pressure by the bleed
nipple as stated did get the vehicle mobile again but the problem in the first
was traced to a malfunction in the release valve of the brake servo not letting
air into the chamber when the brakes were released.  Swapped out the servo and
no further trouble - DID NOT REPLACE THE MASTER CYLINDER.

Second vehicle with similar problems had a leaky master cyl and needed either a
new one or seals.  We stuck a new one on and all was well for about 2 weeks then
another tow in for locked brakes so I swapped the servo and no problems with the
brake till the guy sold the car some 4 years later.

I agree there may be other causes but from experience it would be one of the
first places to look as a seized caliper would NOT lock all 4 wheels.

Brake vacuum servo is leaking................

I am experiencing a problem where the brakes lock up after about four
to five miles of travel.  I was told that the problem could be
resolved by replacing the master cylinder.  I did, but the problem
continues.  The only way to get going, is to release the pressure via
the bleeding valves.  This works sometimes for an eighth of a mile or
sometimes up to ten miles.  I removed all the relays from the ABS unit
with no luck.

Is there someone who has experience this problem?  How was it resolved?