Hummer H3. Manual — part 1099

1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant

thermostat.

J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open
at 90°C (194°F).

J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at
107°C (225°F).

2. Replace the coolant thermostat if it does not operate properly between this temperature

range. Refer to Engine Coolant Thermostat Replacement.

COOLANT HEATER INOPERATIVE

Coolant Heater Inoperative

Step

Action

Yes

No

DEFINITION: The Engine Hot indicator is always ON.

1

Did you perform the necessary inspections?

Go to Step 2

Go to
Symptoms -
Engine Cooling

2

Test the engine coolant heater power supply
cord for an open or short to ground. Refer to
Circuit Testing .
Did you find a condition?

Go to Step 3

Go to Step 4

3

Replace the engine coolant heater power
supply cord. Refer to Coolant Heater
Cord Replacement.
Did you complete the repair?

Go to Step 6

-

4

Inspect for poor connections at the harness
connector of the engine coolant heater.
Refer to Testing for Intermittent
Conditions and Poor Connections and
Connector Repairs .
Did you find and correct the condition?

Go to Step 6

Go to Step 5

5

Replace the engine coolant heater. Refer to
Coolant Heater Replacement.
Did you complete the repair?

Go to Step 6

-

6

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

System OK

Go to Step 2

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

ENGINE FAILS TO REACH NORMAL OPERATING TEMPERATURE

Diagnostic Aids

The engine may fail to reach normal operating temperature due to an intermittent operation of the
thermostat.

Engine Fails To Reach Normal Operating Temperature

PRESSURE CAP TESTING

Tools Required

J 24460-01 Cooling System Pressure Tester. See Special Tools.

Pressure Cap Testing

Step

Action

Yes

No

DEFINITION: Normal coolant temperature readings will be expected to vary from 92-107°
C (198-225°F).

1

Did you perform the Diagnostic System
Check - Vehicle?

Go to Step 2

Go to
Diagnostic
System Check -
Vehicle

2

Verify that the engine fails to reach
normal operating temperature.
Is the engine failing to reach normal
operating temperature?

Go to Step 3

Go to Diagnostic
Aids

3

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

Go to Loss of
Coolant

Go to Step 4

4

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

Go to Step 6

Go to Step 5

5

Replace the thermostat. Refer to Engine
Coolant Thermostat Replacement.
Did you complete the repair?

Go to Step 6

-

6

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

System OK

Go to Step 2

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

1. Remove the pressure cap.

2. Wash the pressure cap sealing surface with water.

Fig. 2: Identifying Cooling System Tester J 24460-01
Courtesy of GENERAL MOTORS CORP.

3. Use the J 24460-01 in order to test the pressure cap. See Special Tools.

4. Test the pressure cap for the following conditions:

Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap.

Maintain the rated pressure for at least 10 seconds.

CAUTION: To avoid being burned, do not remove the radiator cap or

surge tank cap while the engine is hot. The cooling
system will release scalding fluid and steam under
pressure if radiator cap or surge tank cap is removed
while the engine and radiator are still hot.

2007 Hummer H3

2007 ENGINE Engine Cooling - H3

Note the rate of pressure loss.

5. Replace the pressure cap under the following conditions:

The pressure cap does not release pressure which exceeds the rated pressure of the cap.

The pressure cap does not hold the rated pressure.

COOLING SYSTEM LEAK TESTING

Tools Required

J 24460-01 Cooling System Pressure Tester. See Special Tools.

Test Procedure

1. Remove the pressure cap.

2. Test the operation of the pressure cap. Refer to Pressure Cap Testing.

CAUTION: Under pressure, the temperature of the solution in the

radiator can be considerably higher, without boiling.
Removing the radiator cap while the engine is hot
(pressure is high), will cause the solution to boil
instantaneously, with explosive force. The solution will
spew out over the engine, fenders and the person
removing the cap. Serious bodily injury may result.
Flammable antifreeze, such as alcohol, is not
recommended for use at any time. Flammable antifreeze
could cause a serious fire.

CAUTION: In order to help avoid being burned, do not remove the

radiator cap while the engine and the radiator are hot.
Scalding fluid and steam can be blown out under
pressure if the cap is removed too soon.

2007 Hummer H3

2007 ENGINE Engine Cooling - H3