To ascertain whether the piston rings and valves are leaking or not,
first place a block of wood about four inches long upon the guide for
cross-head and against the front cylinder head. Then turn the engine
“over” until the cross-head comes back tight against the block. This
will place the valve of a simple engine in such a position that steam
would be admitted to cylinder through front steam port. If a reversing
engine, throw the reverse lever in the last notch in end of quadrant
that would allow the engine to run “over”. Then take off the back
cylinder head, and open the throttle valve wide. If steam blows out
past the piston, it would indicate that the rings were not tight. In
case steam packing rings are used, they should be refitted or replaced
by new ones. If adjustable rings are used, they should be adjusted to
stop the leak, care being taken not to get them too tight. If the steam
blows out through the back port, the slide valve is not tight and it
will require refitting, as will also the valve seat.
If a very small amount of steam blows through, new rings or adjustment
would not be necessary, as the waste of steam or back pressure
resulting from it would amount to very little.
This test should be tried occasionally with a full head of steam on,
to assure of the piston rings and valve being tight, as leaky pistons
and valves are very wasteful of steam, sometimes causing priming, and
greatly diminishing the power of the engine. Never run your engine with
leaky piston or valve. Have them properly fitted at once.
After making the test, and repairing if necessary, replace the cylinder
head, and be sure to remove the wood block from the guides.