SkyTrak 6042 Service Manual - Manual (Page 201)

7.7 Model 6042 Legacy Origin 7/02
Engine: Cummins 4BT3.9
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, coolant
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 and Specifications.”
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 posi-
tion 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. Level the vehicle, ground the attachment, place the
travel select lever in NEUTRAL (N), engage the
neutral lock lever, engage the parking brake switch
and shut off the engine.
Remove the ignition key. Secure accident prevention
tags to the steering wheel and ignition key switch
(refer to Section 1.5, “Accident Prevention Tag
Usage.”)
2. Unlock, unlatch, and open the side and rear engine
access doors. Allow the engine to cool before
proceeding. Draining the cooling system while the
engine is hot can cause cracks in the engine block.
3. Disconnect the negative (-) battery cable (Fig. 7-2, 1).
Figure 7-2 Disconnect the Negative (-) Battery Cable
WARNING:
DO NOT attempt this
procedure 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.
MA8410
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