Hummer H1 (2006+). Manual - part 180

3-62 Fuel, Emissions, and Exhaust

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ESSENTIAL TOOLS

Procure from Kent-Moore.

Tool No.

Description

J-46594

Fuel Injector Remover

J-38641-B

Diesel Fuel Hydrometer

J-45873

Fuel Return Volume Test Kit

EN-47589

Fuel Pressure Adapter Cap

J-38641-B

J-46594

EN-47589

J-45873

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 4-1

5745804

Section 4   Cooling System

TABLE OF CONTENTS

Automatic Belt Tensioner and Belt Length Scale  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-28
Engine Cooling System

Description   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Diagnosis and Troubleshooting   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Service  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Fan and Clutch Assembly Service   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-27
Geared Fan Drive (GFD) Assembly Service  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-27
Low Coolant Sensor  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-20
Radiator

Lower Hose Replacement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Lower Tube Assembly Replacement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Rear Support Bracket  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
Upper Hose Replacement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

Radiator and Fan Shroud Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-5
Serpentine Belt Replacement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-26
Surge Tank

Overflow Hose Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
Tank-to-Lower Radiator Tube Hose   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18
Tank-to-Radiator Vent Hose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

Thermostat Bypass Hose Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-12
Thermostat Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-21
Water Outlet Pipe Thermostat To Upper Radiator Hose Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-14
Water Pump

Auxiliary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24
Inlet Hose Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

Water Pump and Adapter Plate  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22, 4-24

ENGINE COOLING SYSTEM DESCRIPTION

The cooling system removes excess heat from the engine, engine oil, power steering fluid, transfer case fluid, and transmission
fluid. Some engine heat is beneficial, but excess heat can cause engine oil to break down. If lubrication is significantly reduced, en-
gine damage may result. To keep the oil at the proper temperature, the cooling system dissipates some of the heat produced by the
engine.

The water pump is gear driven by the crankshaft and does not rely on the serpentine belt for operation.

The cooling fan is also driven by the crankshaft through a geared fan drive assembly and viscous connection.

The cooling system is a closed continuous flow system with a pressure cap rated at 15 psi. The coolant travels through the engine
block and circulates around the parts of the engine which generate 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 pre-
vent the engine from being over-cooled, two thermostats monitor the temperature of the coolant and prevent it from being routed to
the radiator until it has reached a temperature high enough to require cooling. The first thermostat begins to open at 180°F (82°C)
and is fully open at 203°F (95°C), the second one opens at 185°F (85°C) and is fully open at 212°F (100°C).

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4-2

Cooling System

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Figure 4-1:   Cooling System Routing

When the thermostat detects the coolant is hot, the thermostat opens, and allows the coolant to be pumped to the radiator where it
is routed through a series of fins and tubes. A fan draws in the outside air to help dissipate the heat before the coolant is recirculated
back through the engine (Figure  4-1).

The fan is driven from the engine crankshaft via the geared fan drive (GFD) and a viscous drive (Figure  4-2). The GFD unit is sup-
ported by the number two cross member, connects to the harmonic balancer of the engine and places the viscous drive and fan as-
sembly on the same plane as and close to the radiator for maximum cooling efficiency. A helical gearset is utilized within the GFD
to change the drive angle from the crankshaft to the fan. 75W-90 synthetic gear lube with friction modifier lubricates the internal
components of the GFD using an integral reservoir and pump. Two constant velocity joints and a torsional drive shaft connect the
GFD to the engine crankshaft at the harmonic balancer. 

Figure 4-2:   Geared Fan Drive Assembly

VISCOUS

DRIVE

CV JOINT/SHAFT

ASSEMBLY

#2 CROSS

MEMBER

MAIN

GFD UNIT

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 Cooling System  4-3

5745804

Figure 4-3:   Cooling System 

The heater provides heat to warm the interior of the vehicle for passenger comfort. Hot coolant leaves the engine and passes
through a heater coil. A fan draws air through the heated coil which heats the air. The air is then channeled through a plenum cham-
ber that directs the flow of the heated air into the passenger compartment. 

If the engine is generating more heat than the cooling system can effectively dissipate, there may be a coolant or cooling system
problem. The engine temperature sending unit transmits a signal indicating the coolant temperature to the temperature gauge on the
instrument panel to let the driver know that the system should be serviced as soon as possible. Engine coolant is added to the sys-
tem through the filler cap in the surge tank. After adding or refilling the cooling system, open the valve on the radiator and bleed
the air from the system.

Like the radiator, the transmission oil/transfercase coolant cooler also uses a series of fins and tubes to dissipate heat from fluid.
The upper half of the cooler dissipates heat from the engine coolant that is circulated through the transfercase cooler while the
lower half cools transmission fluid (Figure  4-3). 

The transmission fluid is cooled by the bottom half of the split cooler. Transmission fluid flows from the transmission oil outlet to
the bottom half of the oil cooler where it returns to the transmission.

The bottom of the transmission torque converter housing provides for the direct mounting of a control main filter and two ports to
facilitate the attachment of the oil cooler lines. The transmission cooler lines connect to a aluminum block on there way to the
cooler. This block houses a pressure/thermal by-pass valve that directs the cooler circuit fluid back to the transmission until operat-
ing temperature is reached. This provides for quicker warm up of the transmission fluid.

The thermal wax element in the valve will start to move up at around 150°. By 180° the valve and seat have closed off the center
port and all fluid is directed to the cooler. The owner would be alerted of an overheat condition of the transmission by the gauge
and the warning light on the dash. A technician should inspect and clean this valve and block during a transmission replacement or
major overhaul. Proper cooler flushing techniques with the J45096 is mandatory with encrypted code documentation on the repair
order. Proper hook up location of the cooler flusher lines is the exit and entrance lines from the block to the cooler. The cooler lines
from block to transmission also need to be flushed. The unit is serviced as an assembly. Check the most current service information
for procedures

.

The separate smaller oil cooler, mounted to the number one cross member, is used to cool the power steering fluid (Figure  4-3).

Two fluid returns are used: one from the hydro-boost and one from the power steering gear. Fluid flow through the hydro-boost is
never completely restricted during braking. The hydro-boost incorporates a fluid return to release the hydraulic pressures used
when applying the brakes (see Section 8 for service procedures).

RADIATOR

SHROUD

FAN

DRAINCOCK

WATER

PUMP

AIR CONDITIONING

CONDENSER

(IF EQUIPPED)

ENGINE OIL/

OIL COOLER

POWER

STEERING

OIL

COOLER

TRANSMISSION

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