The brake valve chest assembly was taken apart to find out why it was laking steam. We found the valve stems (square on end) were not actually round, but oval. Shows the danger of using CNC and circle-interpreting a shaft-CNC does not produce a truely round shaft. I replace the old stiff O-ring and hope it will conform to the oval shaft and stop the leaking.
Octover 2013 update: the valve assembly started out okay, but after several hours of use, started leaking again. It also started leaking between the two halves of the assembly.