ARMY TM 9-6115-604-12
NAVY NAVFAC P-8-633-12
c. Install.
(1) Bolt the replacement fan Idler arm and pulley assembly (22) through the pivot arm support (49) to the engine
block flange.
(2) Install the ribbed V belt (51) in accordance with paragraph 3-12.
(3) Install the shroud and grill assemblies onto the radiator assembly in accordance with paragraph 4-61.
(4) Reinstall the water filter elements and open valve on water filter head.
4-63. MAINTENANCE OF THE ENGINE PREHEAT. The engine preheat assembly (Figure 4-46) is mounted to the skid
base under the engine The preheat system heats the engine coolant to about 100 to 120°F (38 to 49 C) when the engine
is not operating.
a.
Inspect. Inspect heater assemblies H101, H102 (33, Figure 4-46) for loose mountings, loose electrical
connections, loose hose assemblies on the pump, and damage Inspect hoses for loose connections, leakage,
wear or deterioration. Check fittings for loose connections or damage.
b.
Remove.
(1) Close all three shutoff valves (2 and 11, Figure 4-46). Set MAINTENANCE LOCKOUT switch S100 to
MAINTENANCE.
(2) Tag and disconnect wiring to thermostat sensing units (40) and heating elements (34) on heater assemblies
H101 and H102 (33).
(3) Disconnect hose assemblies (19) from heater assemblies H101 and H102 (33) by loosening straight adapters
(20) at ends of hose assemblies (19). Detach center hose assembly (25) and associated plumbing hardware
from the heater assemblies by loosening nipple (22) and adapter (24) from thermostat burrs (41) on heater
assemblies (33). Cap all hose assemblies to prevent coolant contamination.
(4) Remove hose assemblies (6, 19, and 25) from engine block plumbing only if they are damaged or
deteriorated. Remove by loosening hose adapters (7, 20, and 26) from attached plumbing hardware.
(5) Remove heater assemblies H101 and H 102 (33) by removing capscrews (28), nuts (29), and lockwashers
(30) holding heater assemblies to mounting brackets (32). Slide out heater assemblies from beneath brackets.
(6) Remove nut (38), fill cap (39), thermostat sensing unit (40), and thermostat burr (11) as a subassembly from
each heater assembly (33), and test in accordance with step c, below.
(7) Remove heating elements (34) from heating tank (46) by unscrewing, and test in accordance with step c,
below.
c.
Test
(1) Set multimeter on RX1 scale and connect across contacts of thermostat unit.
(2) Using a standard thermometer to track the temperature, put the thermostat unit into a container of engine
coolant at room ambient temperature. The multimeter should show zero ohms (continuity), indicating that the
thermostat contacts are closed.
(3) Raise the temperature of the engine coolant to 120°F (48°C) The multimeter should show infinite ohms
indicating that the thermostat contacts have opened.
(4) Allow the coolant to cool down to 100F (380C). The contacts should close again and the multimeter should
show zero ohms (continuity).
(5) Set multimeter to RX100 scale and connect across heating elements (34) Resistance must be between 8 and
13 ohms.
4-127
