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 TM 55-1905-217-34
(7) With the connecting rod and piston removed from the cylinder block, reassemble the bearing cap and lower
bearing shell to the connecting rod.
b. Disassembly.
(1) Secure the connecting rod (12, fig. 3-72) in a vise equipped with soft jaws and remove the piston rings (4) with
tool J 8128.
(2) Punch a hole through the center of one of the piston pin retainers (1) with a narrow chisel or punch and pry the
retainer from the piston. Use care to prevent damage to the piston and bushings.
(3) Withdraw the piston pin (5) and free the piston (3) from the connecting rod (12).
(4) Drive the remaining piston pin retainer out from the inside with a brass rod or other suitable tool.
(5) The piston pin bushings may be removed with tool set 1513-02 by placing the piston in holding fixture J-1513-
1. Make sure bushing bore is in alinement with the hole in the base of the fixture.
(6) Drive the bushings (2) out of the piston with remover J 1513-3 and handle J 1513-2.
(7) Clamp the upper end of the connecting rod in holder J 7632 so the bore in the bushings is in line with the hole
in the base of the holder.
(8) Set bushing remover J 1513-3 in connecting rod bushing, insert handle J 1513-2 in remover and drive bushings
(10) from the rod.
(9) If necessary to replace the spray nozzle, remove old nozzle as follows:
(a) Remove piston pin bushings.
(b) Insert spray nozzle remover J-8995 through the upper end of the connecting rod and insert the pin in
the curved side of the remover in the opening in the bottom of the spray nozzle.
NOTE
The spring pin in the lower end of the drilled passage in the connecting rod is not serviced
separately, and it is not necessary to remove it when replacing the spray nozzle.
(c) Support the connecting rod and spray nozzle remover in an arbor press.
(d) Place a short sleeve directly over spray nozzle.
(e) Press the nozzle out of the connecting rod.
(f) Remove the spray nozzle removing tool.
c. Cleaning.
(1) After removing the piston rings from the piston and the piston for the connecting rod, clean the parts with
solvent, (FED. SPEC. PD-680) and dry them with compressed air. If the solvent does not remove the carbon deposits,
use a chemical solvent which will not harm the piston pin bushings or the tin plate on the piston.
(2) The upper part of the piston, including the compression ring lands and grooves, is not tin plated and may be
wire-brushed to remove any hard carbon. However, care must be taken to avoid damaging the tin plating on the piston
skirt. Clean the ring grooves with a piece of used compression ring that has been ground to a bevel edge or another
suitable tool.
(3) Clean the cooling surfaces on the inside of the piston and the oil return holes in the lower half of the piston
skirt. Exercise care to avoid enlarging the holes while cleaning them.
(4) Clean the connecting rods and piston pins with cleaning solvent FED. SPEC. PD-680 and dry with
compressed air.
d. Inspection and Repair.
(1) If the tin plate on the piston and the original grooves in the piston rings are intact, it is an indication of very little
wear.
(2) Excessively worn or scored pistons, rings and cylinder liners may be an indication of abnormal maintenance or
operating conditions and these conditions should be corrected as soon as possible.
(3) Examine the piston for score marks, cracks, damaged ring groove lands, or indications of overheating. A
piston with light score marks which can be cleaned up may be reused. Any piston that has been severely scored,
overheated, or burned must be replaced. Indications of over- heating or burned spots on the piston may be the result of an
obstruction in the connecting rod oil passage, which interrupted the flow of oil to the spray nozzle.
(4) Check the cylinder liner and block bore for excessive out-of-round, taper, or high spots which could cause
piston failure.
(5) Other factors that contribute to piston failure include oil leakage into the air box, oil pullover from the air
cleaner, dribbling injectors, combustion blow-by and low oil pressure (dilution of the lubricating oil).
(6) If the piston is to be reused, measure the piston pin bushings and the piston pin. The inside diameter of a new
bushing in the piston is 1.5025 inches to 1.5030 inches, and the outside diameter of a new piston pin is 1.4996 inches to
1.5000 inches. The piston pin-to-bushing clearance with new parts is .0025 inch to .0034 inch. A maximum clearance of
.010 inch is allowable with worn parts.
(7) Inspect rod and piston pin for visible fractures (hairline). Any detectable fractures require that the rod or pin be
replaced.
(8) Examine the spray nozzle at the upper end of the connecting rod to make sure the holes are open. Blow dry
compressed air through the drilled oil passage in the rod to be sure it is open.
3-100
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