Testing Valves With the locomotive in steam:

1. Close the Regulator.
2. Open the Draincocks.
3. Place the reverser into mid-gear.
4. Set the piston of the cylinder to be tested on mid-stroke (In this position the valve covers both front and back ports).
5. If the locomotive has brakes apply them. If not, ensure that the locomotive will not move if the regulator is opened.
6. Crack the regulator open.
   If steam issues from the front draincock then the valve front is leaking steam.
   If steam issues from the back drain cock then the valve back is leaking steam.
   If both drain cocks issue steam then the whole valve seating is faulty.
   No steam from either cock indicates that the valve is perfect.

Testing Pistons

Repeat steps 1, 3, 4, 5 from 'Testing Valves' above (This time the draincocks are closed)

• Crack the regulator open and move the reverser slowly towards full forward gear. (The valve will gradually admit steam to the piston)
• If an increasing blow is heard at the chimney, but which ceases as the reverser is restored to mid-gear, then a blow past the piston is indicated.
• Repeat the whole sequence for the opposite cylinder.