I have an update from the mechanic.  There was no brakes on the van this
morning when it was moved into the bay and put on the rack.  No leaks could
be found anywhere.  The bled the system some and the brakes worked normally.
 His guess is that there is water in the brake fluid and the water boiled
(it was a hot day which didn't help) and thus lost the ability to work
properly.  They are going to do some more testing but for right now, the
brake fluid is going to be replaced.  It is my guess that the master is
still the original one.  It has never been changed since obtaining the van
and that was years ago.  The van is a 1984GL with a manual trans.  Still
getting 20MPG and can accelerate up a 6 degree grade from 40 to 70 mph in
4th gear.  I have received some ideas (thanks) on what could have been the
problem and welcome any additional ideas/inputs.

William