Not sure, maybe reliving steam pressure off the cylinders while the engine is idle? They did tell me that there is plans to reopen the silver mines next year...........BOOOM!!!!!!!/DesktopModules/NTForums/themes/mls/emoticons/laugh.gif
yes stepping on the snifter/drifting valves is to release pressure on the valve chests, could also be done on piston valve loco's by opening the cylinder drains. Usually only on D-valves must you open the drifting valves if they do not drop when the cylinder cocks are opened.