TM-9-2320-272-24-4
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 4 OF 4
JUNE 1998
TM-9-2320-272-24-4 - Page 172 of 836
TM 9-2320-272-24-4
5-26. PISTON AND CONNECTING ROD MAINTENANCE
THIS TASK COVERS:
a. Removal
b. Disassembly
c. Cleaning and Inspection
d. Assembly
e. Installation
INITIAL SETUP:
APPLICABLE MODELS
M939A2
SPECIAL TOOLS
Engine barring tool (Appendix E, Item 43)
Ring compressor (Appendix E, Item 32)
TOOLS
General mechanic’s tool kit (Appendix E, Item 1)
Keystone gauge (Appendix E, Item 54)
Inside micrometer (Appendix E, Item 82)
Outside micrometer (Appendix E, Item 80)
Vernier calipers (Appendix E, Item 159)
Torque wrench (Appendix E, Item 144)
Depth gauge (Appendix E, Item 81)
Feeler gauge
Soft-headed hammer
MATERIALS/PARTS
Piston rings (Appendix D, Item 518)
Two retaining rings (Appendix D, Item 539)
Connecting rod bearing (Appendix D, Item 40)
Lubricating oil (Appendix C, Item 50)
Plastigage (Appendix C, Item 55)
REFERENCES (TM)
TM 9-2320-272-24P
EQUIPMENT CONDITlON
• Cylinder head removed (para. 4-41).
• Oil pan and suction tube removed (para. 4-47).
NOTE
All piston assemblies are replaced the same way. This procedure
covers replacement of one piston assembly.
a. Removal
1.
Using engine barring tool, rotate crankshaft (6) to lower pistons (1) enough to remove all carbon
from upper inside wall of each cylinder (3).
2.
Remove two nuts (8) from screws (5) and connecting rod cap (7).
3.
Using soft-headed hammer, tap screws (5) and remove connecting rod cap (7) from crankshaft (6).
CAUTION
Use a tape-protected tool to push piston from cylinder block.
Failure to do so may cause damage to cylinder liners.
NOTE
Assistant will help with step 4.
4.
Using tape-protected tool, push connecting rod (2) and piston (1) from engine block (4).
b. Disassembly
CAUTION
Pistons, connecting rods, and connecting rod caps must be kept together
as an assembly. Missing parts may cause damage to equipment.
1.
Remove two retaining rings (12) from bore of piston (1). Discard retaining rings (12).
2.
Remove piston pin (13) and connecting rod (2) from piston (1).
3.
Remove ring (9), compression ring (10), and oil ring (11) from piston (1). Discard rings (9), (10),
and (11).
5-166
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