TM-9-2320-272-24-3
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 3 OF 4
JUNE 1998
TM-9-2320-272-24-3 - Page 58 of 799
TM 9-2320-272-24-3
4-52. AIR COMPRESSOR MAINTENANCE (Contd)
1.
Install retaining ring (17) in groove of piston pin bore (19).
Do not drive piston pin into bore. Damage to piston may result.
It may be necessary to heat piston in hot water to install piston
pin.
2.
3.
4.
Lubricate piston pin bore (19) with clean engine oil.
Install connecting rod (2) and piston pin (18) on piston (1) with retaining ring (17).
Install new oil ring expander (16) and two new oil rings (15) on bottom groove of piston (1). Ensure
gaps of oil ring expander (16) and oil rings (15) are offset 180° from each other and 80° from piston
pin bore (19).
5.
Install new intermediate (14) and new top (13) compression rings on grooves of piston (1). Ensure
compression rings (13) and (14) are installed with word TOP facing up, so gaps are 180° from each
other and 80° from piston pin bore (19).
6.
7.
8.
9.
10.
Lubricate piston (1) and piston bore (3) of compressor crankcase (4) with clean engine oil.
Using ring compressor, install piston (1) and connecting rod (2) in compressor crankcase (4).
Lubricate crankshaft (10) with clean engine oil and install in soft-jawed vise.
Install support (9), thrust washer (2), and spacer (22) on crankshaft (10).
Position drive gear (8) on crankshaft (10) and install with washer (23) and screw (20). Tighten
screw (20) 95 lb-ft (129 Nžm).
11.
Remove crankshaft (10) from soft-jawed vise.
12.
Position new gasket (11) on support (9).
Use care when installing crankshaft into connecting rod to avoid
damage.
13.
14.
15.
16.
17.
Lubricate crankcase bushing (24) with clean engine oil.
Position piston (1) at 80° before or after top dead center.
Insert crankshaft (10) and support (9) in compressor crankcase (4) and connecting rod (2).
Turn drive gear (8) to rotate crankshaft (10) until seated in connecting rod journal bore (12) and
crankcase bushing (20).
Install new gasket (11) and support (9) on compressor crankcase (4) with four washers (6),
screws (7), and two new screw-assembled lockwashers (5). Tighten screws (7) and screw-assembled
lockwashers (5) 30-35 lb-ft (41-47 N•m).
4-322
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