Hummer H1 Service Manual page 184

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Section 4 Cooling System
Engine Cooling System
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
Diagnosis and Troubleshooting. . . . . . . . . . . . . . . . . . . . . .4-3
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
Fan and Clutch Assembly Service . . . . . . . . . . . . . . . . . . . . . . .4-16
Low Coolant Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-12
Radiator
Lower Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9
Lower Tube Assembly Replacement . . . . . . . . . . . . . . . . .4-10
Rear Support Bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7
Shroud Shield Assembly Replacement . . . . . . . . . . . . . . . .4-7
Upper Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . .4-9
Radiator and Fan Shroud Assembly . . . . . . . . . . . . . . . . . . . . . .4-4
ENGINE COOLING SYSTEM DESCRIPTION
The cooling system removes excess heat from the engine, en-
gine oil, power steering fluid, transfer case fluid, and transmis-
sion fluid. Some engine heat is beneficial, but excess heat can
cause engine oil to break down. If lubrication is significantly
reduced, engine damage may result. To keep the oil at the
proper temperature, the cooling system dissipates some of the
heat produced by the engine.
Figure 4-1: Automatic Belt Tensioner and Belt
Length Scale
05745159
TABLE OF CONTENTS
Serpentine Belt Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Surge Tank
Thermostat Bypass Hose Replacement . . . . . . . . . . . . . . . . . . . 4-8
Thermostat Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Water Crossover Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Water Pump
Water Pump and Adapter Plate . . . . . . . . . . . . . . . . . . . . 4-13, 4-14
A serpentine belt drives the water pump which pumps coolant
through the cooling system. Proper belt tension must be main-
tained at all times for the proper operation of the cooling sys-
tem. This is accomplished by an automatic belt tensioner
located at the front of the engine next to the generator
(Figure 4-1). The amount of belt stretch may be determined
with the scale located on the arm or the belt tensioner. If the ar-
row on the arm exceeds the parameters indicated, replacement
is required.
NOTE: Inspection of a multiple ribbed serpentine belt may re-
ARROW veal cracks in the belt ribs. These cracks will not impair belt
performance and are not a basis for belt replacement. If any
belt ribs are missing, the belt should be replaced.
SCALE The cooling system is a closed continuous flow system with a
pressure cap rated at 15 psi. Coolant travels through the engine
block and circulates around the parts of the engine which gen-
erate heat: the cylinders, cylinder heads, combustion chambers,
valve guides, valve seats, etc. As coolant is routed through the
engine block, heat is transferred from the engine to the coolant.
The water crossover on diesel engines collects coolant from the
cylinder heads and channels it to the thermostat housing. To
prevent the engine from being over-cooled, the thermostat
monitors the temperature of the coolant and prevents it from
being routed to the radiator until it has reached a temperature
high enough to require cooling (Figures 4-2 and 4-3). The ther-
mostat begins to open at 190°F (88°C) and is fully open at
212 °F (100°C).
Overflow Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . 4-11
Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Tank-to-Lower Radiator Tube Hose. . . . . . . . . . . . . . . . . . 4-12
Tank-to-Radiator Vent Hose . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
Inlet Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
4-1