Hummer H1 (2002+). Manual - part 46

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 Fuel, Emissions, and Exhaust  3-45

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5745159

ESSENTIAL TOOLS

Procure from Kent-Moore.

Tool No.

Description

J–29075-AMG

Fuel Injector Pressure Test Tool

J–29872-A

Injection Pump Adjusting Tool (used with ratchet handle)

J–29873

Fuel Injector Socket (30mm)

J–29698-A

Injection Line (flare nut) Wrench, 3/4

J–28552-A

Fuel Pressure Gauge

J–38641-B

Diesel Fuel Hydrometer

J–34151

Housing Pressure Adapter

J–41711

Injection Pump Timing Wrench, 6.5 Turbo (not shown)

J–28552-100

Adapter, Fuel Line

J–29075-AMG

J–29872-A

J–29873

J–41089

J–29079-125

J–41516-A

J–29698-A

J–28552-A

J–38641-B

J–34151

3-46

Fuel, Emissions, and Exhaust

___________________________________________

®

SPECIAL TOOLS

Procure from Kent-Moore.

Tool No.

Description

J–26925

Mag-Tac Engine Tachometer

J–26925

 

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 4-1

  

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05745159

 

Section 4   Cooling System

 

TABLE OF CONTENTS

 

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

Serpentine Belt Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
Surge Tank

Overflow Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . 4-11
Replacement  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Tank-to-Lower Radiator Tube Hose. . . . . . . . . . . . . . . . . . 4-12
Tank-to-Radiator Vent Hose . . . . . . . . . . . . . . . . . . . . . . . . . 4-8

Thermostat Bypass Hose Replacement . . . . . . . . . . . . . . . . . . . 4-8
Thermostat Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13
Water Crossover Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
Water Pump

Inlet Hose Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11

Water Pump and Adapter Plate . . . . . . . . . . . . . . . . . . . .  4-13, 4-14

 

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

 

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-

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.

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).

ARROW

SCALE

 

4-2

Cooling System

 

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Figure 4-2:   Cooling System Routing

 

When the thermostat detects the coolant is hot, the thermostat
opens allowing coolant to be pumped to the radiator where it is
routed through a series of fins and tubes. A fan draws in out-
side air to help dissipate the heat before the coolant is recircu-
lated back through the engine (Figure 4-3).

 

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
chamber that directs the flow of the heated air into the passen-
ger compartment. 

If the engine is generating more heat than the cooling system
can effectively dissipate, there may be a coolant or cooling sys-
tem 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 system through the filler cap in the surge tank.
After adding or refilling the diesel engine cooling system, open
the valve on the water crossover and bleed the air from the sys-
tem.

Like the radiator, the oil cooler also uses a series of fins and
tubes to dissipate heat from fluid. The lower half of the oil
cooler dissipates heat from the engine oil while the upper half
cools transmission fluid. 

Engine oil flows from the left rear of the engine block to the
bottom half of the oil cooler, then returns to the engine block.

 

NOTE: 

 

To ensure an accurate engine oil level measurement

check the engine oil within 1 to 2 minutes after shut down.

The transmission fluid is cooled by the top half of the split oil
cooler. Transmission fluid flows from the transmission oil out-
let to the top half of the oil cooler, then to the inside of the
transfer case, where it returns to the transmission  (Figures 4-2
and 4-3). The transmission fluid that passes through the trans-
fer case does not mix with the transfer case fluid, but flows
through a separate oil (secondary) cooler located within the
transfer case.

A transmission cooler bypass valve is positioned between the
transmission and transfer case cooler in the fluid line. The unit
is rigidly mounted to the frame rail and is connected in parallel
by hoses to the transmission cooler. The valve consists of a
housing with inlet and outlet fittings, and an internal flow con-
trol valve, spring loaded in the closed position. The valve is de-
signed to begin opening at approximately 20 psi and be fully
open by 30 psi allowing fluid to bypass the transmission cooler
and regulate fluid pressure in the cooler.

At low temperatures, fluid viscosity and pressure are typically
high. By allowing fluid to bypass the cooler at low tempera-
tures the transmission warms to normal operating temperature

HEATER

SURGE TANK

THERMOSTAT

OIL COOLER

RADIATOR

TRANSFER CASE

OIL COOLER

TRANSMISSION OIL

COOLER BYPASS

VALVE

ENGINE TEMPERATURE

SENDING UNIT

WATER

CROSSOVER

RADIATOR

SHROUD

FAN

DRAINCOCK

WATER

PUMP

AIR CONDITIONING

CONDENSER

(IF EQUIPPED)

ENGINE OIL/

OIL COOLER

POWER

STEERING

OIL 

COOLER

TRANSMISSION