Front Air Brake Issues

[akav8r]

Currently working on front brakes. After a short trip to the shop I
work on my Bird in I noticed that the front hubs were warmer than
they should be. After further looking I discovered that the front
brakes are dragging slightly. After even further investigation I
have determined that the pancake (air can) for both front brakes are
not completely releasing their air pressure. I understand that it
is possible for this to happen if the front brakes are not properly
adjusted however the problem continues even after they(pancakes) are
disconnected from the shoe arm. For this test the pancake/air can
has been completely removed from the frame and is simply hanging
from the rubber brake line - no kinks. I have replaced the
exhaust/dump valve (QR1 I think) for the front brakes with no
change. I gently probed the diaphram in the dump valve through the
exhaust port and the air pressure immediately dumps releasing the
pancake/air can. I have also removed the air can and tested it with
an air compressor and it extends with pressure and immediately
releases when air pressure is released. I have now learned there is
another valve of some type between the dump valve and the foot
treadle valve. Is this some sort of check valve or something else?

Help from anyone with experience, information, or ideas on this
problem would be greatly appreciated. Also if anyone has brake/air
diagrams I would like to have a copy if able.

Once again THANKS in advance.
Wendel, GA
82 FCSB35