TM 55-203
(c) When a new ring is to be fitted, place
ring in the body cylinder; a snug fit should be obtained.
Check alignment of piston and position outside surface
of ring into ring groove. Turn the ring the full length of
the circumference and note if ring is restricted from
turning freely. If ring does not turn free, remove burrs or
repair as required. Position ring in groove. A slight drag
should be felt when, turning the ring in the groove.
Note. When fitting new lap joint rings, they
must be carefully installed with the narrow bearing
surface of the scarf towards the brake pipe side.
(d) If the wick which runs from the small
crescent-shaped recess in the bottom of the ring groove
to the oil reservoir is damaged, it must be replaced. A
new wick is approximately 5 3/4 inches long. To
facilitate assembly, a special wick is available having
bare wire on one end for about 2 1/4 inches. If specially
prepared wicks are not available, bare the wire by
burning. Start the wire down through the wick hole and
pull the wick through the hole until about 1/2 inch end is
left in the ring groove. Bend the end of the wick across
the middle or breather hole and anchor in the last hole in
the recessed ,section at the bottom of the ring groove.
Cut the bare wire off the wick and wind it in a
counterclockwise direction around the oil reservoir. The
free end of the wick must not obstruct or come in
Figure 8-21. Service portion cover and release
contact with the 1/32-inch-diameter breather hole
insuring parts.
located adjacent to the wick hole in the oil reservoir.
(c) Thoroughly clean all parts with an
(e) When the piston ring and its groove are
organic solvent type cleaner to remove all dirt, oil, gum,
thoroughly clean and dry, position the end of the ring
and grease. Do not use an alkaline cleaning solution.
above the lubricating hole in the bottom of the ring
Lubricate the entire surface with one drop of lubricating
groove. Raise the end of the ring and make sure that
oil (SAE-20).
the lubricating wick is flat on the bottom of the recessed
(6) Inspection and lubrication of self-oiling
portion of the ring groove. The wick must not touch the
piston
ring or the mouth of the breather hole.
(a) Clean the piston ring and its groove by
dipping the piston in cleaning fluid and then moving the
(f) Remove the oil plug which seals the oil
ring around in the groove. Repeat the operation until
reservoir and drain the old oil from the reservoir. If the
the groove and ring are thoroughly cleaned.
oil plug is of the hexagon type, insert a capscrew into
the outer tapped opening so it will not be distorted with
Note. An early type of self-oiling piston,
the wrench when being removed. Use care to avoid
having two holes drilled in the piston head near the top
twisting the piston stem. If the oil plug has been
of the piston, must not be submerged in cleaning fluid.
tightened excessively, tap lightly or use some other
For this type of piston, see instructions in (7) below.
means in loosening it rather than by means of a wrench
and vise, which will cause damage.
(b) Where rings are stuck with dirt too
tightly to be moved in the groove, soak the ring in
penetrating oil and then tap the ring gently with a
hardwood block to drive it flush with the top edge of the
groove. Start the tapping at one side of the ring joint
and progress around the piston in short steps until the
ring is loosened sufficiently to be moved in the groove.
If this procedure will not loosen the ring, it is evident that
the groove is binding and must be reconditioned and a
new ring fitted.
8-24
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