(2) Secure ST-1257-6 vacuum cup to vacuum pump suction hose.
(3) Grease ST-1257-3 O-ring and insert into vacuum cup.
(4) Insert power plug in 110 vac wall outlet.
(5) Place vacuum cap over valve head. O-ring on cup should seat on flat surface of head.
(6) Turn pump valve to open position.
(7) Place toggle switch on. This provides power to motor driven vacuum pump.
(8) Operate pump until vacuum gage indicates 25 in. (635 mm) vacuum.
(9) Close dump valve and place toggle switch off.
(10) Time drop off of vacuum as follows:
(a) Begin timing when gage hand reaches 18 in. (457.2 mm).
(b) Stop timing when hand reaches 8 in. (203.2 mm).
(c) If elapsed time is less than 10 seconds, valve seat is unsatisfactory.
(11) Tap stem end of valve with softfaced mallet and retest.
(12) If valve seat is still unsatisfactory:
(a) Check for leaking connection in tester by placing vacuum cup against clean window pane or any
other flat surface. If vacuum drop occurs, check tester for loose connections.
(b) Check valve and seat face contact area to ensure it is free of dirt particles.
It is possible to have leak around valve seat insert and mistake that leak for valve
seating area leakage.
(13) Apply grease around outside edge of insert to make a grease seal.
(14) Retest valve.
(15) Inspect grease seal for a break indicating air leakage is between wall of counterbore and outside edge of
(a) Stake insert and retest.
(b) If unsatisfactory leak still exists around insert, remove insert and install next oversize.