Hummer H3. Manual — part 1097

ENGINE OVERHEATING

Diagnostic Aids

The engine may overheat due to an intermittent operation of the thermostat.

Engine Overheating

Step

Action

Values

Yes

No

DEFINITION: Engine temperature lamp comes ON and stays ON or the temperature gage
shows hot or coolant overflows from the coolant recovery reservoir onto the ground while
the engine is running.

1

Did you perform the Diagnostic
System Check - Vehicle?

-

Go to Step 2

Go to
Diagnostic
System
Check -
Vehicle

2

Inspect the coolant recovery reservoir
for low coolant.
Is there a loss of coolant?

-

Go to Loss
of Coolant

Go to Step 3

3

Start the engine and allow to reach
normal operating temperature.Does
the engine begin to exceed the
specified value?

IMPORTANT:

Do not allow the engine temperature to
exceed the specified value.

107°C

(225°F)

Go to Step 4

Go to
Diagnostic
Aids

4

Inspect for loose, damaged, and/or
missing of the following:

The A/C condenser seals

The front air deflector

The side seals

Repair the system as necessary.
Does the engine still overheat?

-

Go to Step 5

Go to Step

17

Using the J 23688 Coolant and
Battery Fluid Tester, test for

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

5

insufficient coolant concentration. See
Special Tools.
Is the coolant protection greater than
the specified value?

-37°C (-34°

F)

Go to Step 6 Go to Step 7

6

Correct the coolant concentration as
necessary.
Does the engine still overheat?

-

Go to Step 7

Go to Step

17

7

Inspect for obstructed radiator air
flow or bent radiator fins.
Is the radiator air flow obstructed?

-

Go to Step 8 Go to Step 9

8

Clean the radiator. Refer to Radiator
Cleaning.
Does the engine still overheat?

-

Go to Step 9

Go to Step

17

9

Inspect the drive belt tensioner. Refer
to Drive Belt Tensioner Diagnosis .
Is the drive belt tensioner working
properly and is the tension correct?

-

Go to Step

11

Go to Step

10

10

Replace the drive belt tensioner. Refer
to Drive Belt Tensioner
Replacement .
Does the engine still overheat?

-

Go to Step

11

Go to Step

17

11

Inspect the thermostat for proper
operation. Refer to Thermostat
Diagnosis.
Does the thermostat operate properly?

-

Go to Step

13

Go to Step

12

12

Replace the thermostat. Refer to
Engine Coolant Thermostat
Replacement.
Does the engine still overheat?

-

Go to Step

13

Go to Step

17

13

Inspect for an inoperative fan clutch.
Refer to Fan Clutch Diagnosis.
Does the engine still overheat?

-

Go to Step

14

Go to Step

17

14

Inspect for blocked cooling system
passages.
Are the cooling system passages
blocked?

-

Go to Step

15

Go to Step

16

15

Replace the radiator. Refer to
Radiator Replacement.

-

Go to Step

Go to Step

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

LOSS OF COOLANT

Loss of Coolant

Does the engine still overheat?

16

17

16

Replace the engine water pump. Refer
to Water Pump Replacement.
Did you complete the repair?

-

Go to Step

17

-

17

Operate the system in order to verify
the repair.
Did you correct the condition?

-

System OK Go to Step 2

Step

Action

Yes

No

DEFINITION: The cooling system is loosing coolant either internally or externally.

1

Were you sent here from Symptoms or
another diagnostic table?

Go to Step 2

Go to
Symptoms -
Engine Cooling

2

Repair any present DTCs. Refer to
Diagnostic System Check - Vehicle .
Is the action complete?

Go to Step 3

-

3

Inspect the coolant level.
Is the coolant at the proper level?

Go to Step 6

Go to Step 4

4

Fill the cooling system to the proper level.
Refer to Cooling System Draining and
Filling (Static Fill) or Cooling System
Draining and Filling (Vac-N-Fill).
Is the action complete?

Go to Step 5

-

5

If the engine is suspected to have a coolant
leak into a cylinder, the coolant can
hydraulically lock the engine.
Does the engine crankshaft rotate?

Go to Step 6

Go to Step 28

6

Engine overheating can cause a loss of
coolant.
Is the engine overheating?

Go to Step 29

Go to Step 7

7

Extended operation with a low coolant level
can cause engine internal component failure.
Is the engine knocking?

Go to Step 31

Go to Step 8

1. Idle the engine at normal operating

temperature.

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

8

2. Inspect for heavy white smoke coming

out of the exhaust pipe.

Is a heavy white smoke present from the
exhaust pipe?

Go to Step 9

Go to Step 10

9

Coolant in the exhaust system creates a
distinctive, burning coolant odor in the
exhaust.

Condensation in the exhaust system can
cause an odorless white smoke during
engine warm up.

Does the white smoke have a burning coolant
type odor?

Go to Step 30

Go to Step 10

10

With the engine idling, inspect the coolant
recovery system.
Does the coolant recovery system discharge
coolant while the engine is idling?

Go to Step 15

Go to Step 11

11

Visually inspect the hoses, pipes and hose
clamps at the following locations:

Coolant reservoir

Heater core

Radiator

Are any of the hoses, clamps or pipes leaking? Go to Step 20

Go to Step 12

12

Visually inspect the following components:

Block heater

Coolant pressure cap

Core plugs

Cylinder head gaskets

Engine block

Intake manifold

Radiator

Thermostat housing

2007 Hummer H3

2007 ENGINE Engine Cooling - H3