TM 5-3895-359-14&P
Inspection
If the tin-plate on the piston skirt and the original
grooves in the piston rings are intact (no visible wear
step on the lower groove land), it is an indication of very
little wear.
Excessively worn or scored piston skirts, rings or
cylinder liners may be an indication of abnormal
maintenance or operating conditions which should be
corrected to avoid recurrence of the failure. The use of
the correct types and proper maintenance of the
lubricating oil filters and air cleaners will reduce to a
minimum the amount of abrasive dust and foreign
material introduced into the cylinders and will reduce the
rate of wear.
Long periods of operation at idle speed and the use of
improper lubricating oil or fuel must be avoided,
otherwise a heavy formation of carbon may result and
cause the rings to stick.
Fig. 5. Checking Fire Ring Groove in Piston Crown
Keep the lubricating oil and engine coolant at the proper
using Tool J 24599
levels to prevent overheating of the engine.
6. Remove the metal seal ring from the piston crown.
7, Remove the piston pin bushing (bearing).
Cleaning
Clean the piston components with fuel oil and dry them
with compressed air. If fuel oil does not remove the
carbon deposits. use a chemical solvent that will not
harm the tin-plate on the piston.
The piston crown, including the compression ring
grooves, is not tin-plated and may be wire-brushed to
remove any hard carbon. Do not wire-brush the piston
skirt. Clean the ring grooves with a suitable tool or a
piece of an old compression ring that has been ground
to a bevel edge.
Clean the inside surfaces of the piston crown and skirt
and the oil drain holes in the lower half of the piston
skirt. Exercise care to avoid enlarging the holes while
cleaning them.
Glass beading can be used to clean a piston crown.
Mico Bead Glass Shot MS-M (.0029"-.0058") is
recommended. Allowable air pressure is 80-100 psi
(552-689 kPa). After cleaning, do not leave glass beads
in the piston crown.
NOTE
Fig. 6. Installing Seal Ring
Do not attempt to clean the piston
skirt by glass beading, as it will
remove the tinplating.
10-2-80
