TM-9-2320-272-24-1

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 1 OF 4

JUNE 1998
TM-9-2320-272-24-1

  TM-9-2320-272-24-1 - Page 162 of 1015

TM 9-2320-272-24-1
Table 2-2. Mechanical Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
23. ENGINE OVERHEATS AS INDICATED BY ENGINE COOLANT TEMPERATURE GAUGE
WARNING
Extreme care should be taken when removing surge tank filler cap
if temperature gauge reads above 175°F (79°C). Steam or hot
coolant under pressure may cause injury.
Step 1.
Check coolant level (TM 9-2320-272-10).
CAUTION
l
Do not add coolant to engine when hot. Internal damage to
engine could result.
l
On M939A2 series vehicles, ensure drainvalve on aftercooler is
open. Failure to do so may result in damage to equipment.
If coolant level is low, fill to proper level (para. 3-53).
Step 2.
Check engine oil level (TM 9-2320-272-10).
If oil level is low, fill to correct level (LO 9-2320-272-12).
Step 3.
Inspect drivebelts and tensioner (M939A2) for looseness, absence, and worn conditions.
a. If loose, tighten.
b.
Replace drivebelt if worn or damaged (paras. 3-67, 3-68, 3-71, 3-80, 3-81, or 3-236).
Step 4.
Inspect radiator, hoses, hose connections, and drainvalves for leaks.
a.
Tighten loose hose clamps and fittings.
b. Tighten or close drainvalves.
c.
Replace defective cooling system components (chapter 3, section V).
Step 5.
Check cooling system for clogging.
If clogged, flush and clean cooling system (para. 3-53).
Step 6.
Inspect fan for cracked or missing blades.
If blades are cracked or missing, replace fan (para. 3-64 or 3-72).
Step 7.
Check radiator for airflow obstructions.
Remove obstructions from front of radiator (TM 750-254).
Step 8.
Observe fan clutch and actuator for proper operation.
If defective, replace fan clutch and actuator (para. 3-73 or para. 3-74).
Step 9.
Check water pump for leaks and proper operation.
a.
Start engine (TM 9-2320-272-10). Remove surge tank cap and visually check coolant for
proper circulation.
b.
Stop engine. If coolant is seen circulating and temperature is below 175°F (79°C)
replace thermostat (para. 3-65 or 3-66).
NOTE
If STE/ICE is available, perform NG31 - Gauge Test (para. 2-24).
Step 10.
Test temperature gauge for proper operation (TM 9-2320-272-10).
If not correct, notify DS maintenance.
END OF TESTING!
2-74


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