Dieseldude......It is now April 28, 2014, and I am having the exact same issue that you did. I just installed a new master brake cylinder on my 1960 Viking 2 ton, and now the brake pedal is rock hard, and only moves down an inch or so. I loosened the two front bleeder screws, and get no fluid coming out when I hit the brake pedal. When I take the top off the MBCylinder, fluid does squirt upward when I hit the rock hard brake pedal. MBC is not leaking any fuid, and when it sits for a week, there is no loss in fluid.
Did you ever discover what your problem was? I would bet I have the same issue. Do I need to try bleeding the Hydrovac, or could a bad check valve do this?
Many thanks for any suggestions.
dwight
