--In a message dated 4/6/2013 12:01:08 A.M. Central Daylight Time, glpav...@xxxxxxx writes:A drum master cyl. has a 10lb. residual pressure valveGary, Thank You for correcting my error, guess I should not try to answer questions late at night, the residual valve was my first thought as well, here is an article that will help explain it..... roger