TM-9-2320-272-24-2
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 2 OF 4
JUNE 1998
TM-9-2320-272-24-2 - Page 689 of 991
TM 9-2320-272-24-2
Table 4-1. Mechanical Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
9. EXCESSlVE OIL CONSUMPTlON
Step 1. Check for external oil leakage.
Replace or repair as necessary.
Step 2. Replace engine (para. 4-4 or 4-5).
END OF TESTING!
10. AIR CLEANER ELEMENT CLOGGED WITH OIL
Step 1. Clean air cleaner housing and replace element (para. 3-15).
Step 2. Check fluid levels in transmission, transfer case, and fuel tank(s) for signs of overfilling, and
correct as necessary (LO 9-2320-272-12).
Step 3. Trace source of oil through vent line tubes on air inlet stack and check related components.
END OF TESTING!
11. ENGINE KNOCKS (MECHANICAL NOISE)
Replace engine (para. 4-4 or 4-5).
END OF TESTING!
12. EXCESSIVE ENGINE VIBRATION
Step 1. Check for loose or damaged vibration damper.
If loose, tighten. If damaged, replace (para. 4-14 or 4-42).
Step 2. Check for loose or damaged engine mounts (M939A2).
If loose, tighten. If damaged, replace (para. 4-39).
Step 3. Check for loose or damaged flywheel or flywheel ring gear.
If loose, tighten. If damaged, replace (para. 4-15, 4-16, or 4-43).
Step 4. Check fuel injectors for proper operation and adjustment (para. 4-33, 4-34, or 4-56).
END OF TESTING!
13. EXCESSIVE GEAR NOISE
Step 1. Check for loose or damaged flywheel or flywheel ring gear.
If loose, tighten. If damaged, replace (para. 4-15, 4-16, or 4-43).
Step 2. Check backlash of all accessory drive gears (para. 4-21, 4-49, 5-8, 5-9, 5-27, or 5-29).
Step 3. Replace engine (para. 4-5).
END OF TESTING!
FUEL SYSTEM
14. ENGINE IDLE ROUGH, ERRATIC
Step 1. Check for loose or damaged engine mounts (M939A2).
If loose, tighten. If damaged, replace (para. 4-39).
Step 2. Perform malfunction 2.
END OF TESTING!
4-7
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