Lull 944E-42 Service Manual - Manual (Page 210)

Engine: Cummins 4BT 3.9, B4.5T and QSB 4.5T
7.8 Model 644E-42/944E-42 Rev. 6/04
7.6 ENGINE COOLING SYSTEM
The engine cooling system is a closed, pressurized
system that consists of coolant passages in the engine,
plus the oil cooler, thermostat, water pump, engine block
heater, hoses, radiator and radiator overflow bottle. The
engine is cooled by the circulation of coolant through
passages in the cylinder block, engine head and radiator.
Circulation is by thermo-siphon action, assisted by an
impeller-type water pump, driven by a fan belt from the
crankshaft pulley. The water pump bearings are
prepacked with a special grease and DO NOT require
service. Replace a faulty water pump. General engine
cooling specifications and maintenance procedures are
listed in Section 2, “General Information, Specifications
and Maintenance.”
7.6.1 Radiator Pressure Cap
The cooling system is designed to use a radiator
pressure cap to help prevent the coolant from boiling. In
addition, the pressure helps to eliminate the formation of
steam pockets within the engine and ensures coolant
circulation throughout all coolant passageways of the
engine. For a 210° F (99° C) system, use a 13 psi (90
kPa) radiator cap. An incorrect or malfunctioning cap can
result in the loss of coolant and a hot-running engine.
7.6.2 Thermostat Replacement
Before considering thermostat replacement, check the
coolant level, fan belt tension and dash panel
temperature indicator. If the engine seems to take a long
time to warm up, the thermostat may be stuck in the open
position and requires replacement. If the engine runs hot,
check the temperature of the upper radiator hose. If the
hose is not hot, the thermostat may be stuck in the closed
position. If the engine has overheated, performance may
suffer, indicating other damage including a leaking
cylinder head gasket, cracked cylinder head or block,
and/or other internal engine damage.
a. Thermostat Removal
1. Park the vehicle on a firm, level surface. Level the
vehicle, ground the attachment, place the travel
select lever in the (N) NEUTRAL DETENT position,
engage the parking brake switch and shut the
engine OFF.
2. Secure accident prevention tags to the steering
wheel and ignition switch. (Refer to Section 1.5,
“Accident Prevention Tag Usage.”)
3. Unlatch and open the engine cover. Allow the engine
to cool before proceeding. Draining the cooling
system while the engine is hot can cause cracks in
the engine block.
4. If the vehicle has dual batteries, disconnect both
negative battery cables (1 and 2) from both
batteries.
To access the lower battery (3), loosen the knob (4)
far enough so that the lip (5) on the upper battery box
clears the knob. Lift up the upper battery box (6) and
swing it out, so that the box clears the hydraulic tank
support bracket, to gain access to the lower negative
battery cable (1). Disconnect the lower negative
battery cable.
WARNING:
DO NOT attempt this proce-
dure when the engine is hot. Wait for the
engine, muffler, and tailpipes to cool down
before proceeding. Failure to do so could result
in severe burns.
MU0650
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