TM-9-2320-272-23-2

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

TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 2 OF 5

SEPTEMBER 2012

TM-9-2320-272-23-2 - Page 1035 of 1417

REMOVAL (INTERNAL BYPASS)

WARNING

Do not drain coolant when engine is hot. Severe burns may result. Failure to comply may

result in injury or death to personnel.

NOTE

There are two different bypass systems used for M939A2 engines. An identifiable difference

is the thermostat housing for external bypass and internal bypass engines.

1.

Drain three quarts of coolant from oil cooler drain valve (Figure 1, Item 11) into container.

2.

Loosen clamp (Figure 1, Item 3) and remove hose (Figure 1, Item 2) from adapter (Figure 1, Item 4).

3.

Loosen alternator link screw (Figure 1, Item 12).

4.

While supporting alternator (Figure 1, Item 15), remove two screws (Figure 1, Item 13) and washers

(Figure

1, Item 14) from bracket (Figure 1, Item 16). Pivot alternator down and move bracket aside.

5.

Remove four screws (Figure 1, Item 17) and bracket (Figure 1, Item 18) from thermostat housing

(Figure

1,

Item 7).

NOTE

Tag screws for identification in installation.

6.

Remove two screws (Figure 1, Item 1), adapter (Figure 1, Item 4), and gasket (Figure 1, Item 5) from thermostat

housing (Figure 1, Item 7). Discard gasket.

7.

Remove two screws (Figure 1, Item 6), thermostat housing (Figure 1, Item 7), and gasket (Figure 1, Item 8)

from engine block (Figure 1, Item 10). Discard gasket.

CAUTION

Cover coolant passages. Dirt in cooling system will cause overheating and engine failure.

8.

Remove two thermostats (Figure 1, Item 9) from engine block (Figure 1, Item 10).

TM 9-2320-272-23-2

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