TM 10-4320-307-24
4-16
CONNECTING ROD AND PISTON ASSEMBLY REPLACE/REPAIR (CONT).
5.
Visually inspect pistons (1) for cracks or damage in
bowl (2), pin bore (3), or skirt (4). Check for scoring or
evidence of overheating. Slight scoring may be
removed with crocus cloth. Replace cracked, heavily
scored, or damaged pistons.
6.
Visually inspect piston pins (5) for scratches, grooves,
signs of overheating, or other damage.
7.
Visually inspect connecting rod assemblies (6) for
damage. Use magnetic method (Magnaglo) to locate
cracks in connecting rods and caps. Replace rod if
cracked or if I beam section is nicked or chipped,
deeper than 1/32 inch (0.80 mm).
8.
Visually inspect piston pin bushing (7) for damage or
for misalignment of oil passage and bushing oil hole.
9.
Visually inspect connecting rod bolts (8) for thread
damage. Replace bolts with damaged threads. Use
magnetic method (Magnaglo) to locate cracks in bolts.
Replace cracked bolts.
10. Visually inspect connecting rod bearing shells (9) for
grooving or other damage. Replace if damaged.
11. Measure pistons as follows:
a.
Use a ring groove wear gauge (10) to check for
depth wear in top and second ring grooves.
NOTE
The widest part of the tool (shoulder) must not
come in contact with the piston. Replace piston
if shoulder touches piston when tool is inserted
in ring groove.
b.
Use a new piston ring (11) and feeler gauge (12) to
check each of the four ring grooves. Hold a new
ring in groove and try to slide a 0.006 inch (0.152
mm) feeler gauge between ring and groove. If
feeler gauge enters without resistance, there is too
much wear and piston must be replaced.
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