76. Q. How can the blowing of steam past cylinder packing, a valve or
valve strip be distinguished or located?

A. Test for a leaky slide valve, place the engine on the quarter on the
suspected side with the reverse lever in center notch; the valve should
be in the middle of its travel and cover both ports. If steam blows
through the open cylinder cocks on that side, the valve or seat are
defective. A leaky balanced valve strip will allow steam to blow through
the hole on top of the valve into the exhaust port in the seat and very
little steam will come out of the cylinder cock; in some cases with the
valve barely opening a steam port to the exhaust, air will draw in at
the cylinder cock. If there is a drip cock in the exhaust pipe under the
saddle, the steam will blow out there. After testing for leaky valve,
place the engine on about the forward bottom or top back eighth, block
the wheels or set the brakes solid, put reverse lever in corner, open
cylinder cocks and give the engine steam. If steam comes out of both
cylinder cocks, and testing valve shows it is tight, then the packing is
blowing. Cylinder packing should be tested with steam first on one side
of the piston and then on the other.

77. Q. If engine should blow badly and be unable to start the train when
on the right dead center, on which side would be the blow generally?

A. On the left side. If the side standing on the quarter cannot start
the train, the trouble is usually there.

78. Q. If throttle were closed and steam came out of cylinder cocks,
what might be the cause?

A. To test for this, first shut off steam connection to the lubricator;