Hummer H2. Manual - part 1386

Does the fan clutch have more resistance when the engine 
temperature is raised?

Go to 

Step 11

Go to Step 14

10

Tighten the fan. Refer to Fastener Tightening Specifications . 
Is the repair complete?

Go to 

Step 16

-

11

Perform a fan clutch engagement test. 

1. Ensure the engine coolant level is full.  

2. Ensure the cooling fan drive belt tension is correct and not 

slipping.  

3. Position and secure a thermometer between the fan clutch and 

the radiator.  

4. Ensure the cooling fan is disengaged before starting this test.  

5. Sufficiently cover the radiator grille to restrict the air flow. 

6. Start the engine.  

7. Turn the A/C ON.  

8. Operate the engine at approximately 2,000 RPM.  

9. Inspect the thermometer reading when the fan clutch engages. 

10. Do not continue this test if the fan clutch does not engage 

between 85-96° C (185-205° F).  

 
Fan clutch engagement will be indicated by an increase in fan air 
noise, fan speed, and a drop of about 3-10° C (5-15° F) on the 
thermometer reading. 
Did the fan clutch engage between 85-96° C (185-205° F)?

IMPORTANT:

Do not allow engine temperature to exceed 121° C (250° F).

Go to 

Step 12

Go to Step 14

12

Once the fan clutch engages, perform the following steps: 

1. Uncover the radiator grille.  

2. Turn the A/C OFF.  

3. Operate the engine at approximately 2,500 RPM to reduce the 

engine operating temperature.  

4. Remove the thermometer.  

 
Did the engine return to normal operating temperature?

Go to 

Step 13

-

13

As the engine temperature returns to normal, the fan clutch will 
disengage, indicated by a reduction in fan air noise and fan speed. 
Did the fan clutch disengage?

Go to 

Step 16

Go to Step 14

Replace the fan clutch. Refer to Fan Clutch Replacement . 

Go to 

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

REPAIR INSTRUCTIONS 

DRAINING AND FILLING COOLING SYSTEM 

Tools Required 

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J 26568 Coolant and Battery Tester. See Special Tools and Equipment .  

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J 38185 Hose Clamp Pliers. See Special Tools and Equipment .  

Draining Procedure 

1. Follow the steps below in order to remove the surge tank fill cap. 

1. Slowly rotate the cap counterclockwise.  

2. Stop rotating and allow the hissing to stop.  

3. After all the hissing stops, continue turning counterclockwise in order to remove the cap.  

2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.  

3. Place a drain pan under the lower radiator hose.  

4. Using the J 38185 , reposition the lower radiator hose clamp. See Special Tools and Equipment .  

5. Remove the lower radiator hose from the radiator.  

6. Drain the cooling system. 

14 Is the repair complete?

Step 16

-

15

Replace the fan blades. Refer to Fan Replacement . 
Is the repair complete?

Go to 

Step 16

-

16

Operate the fan clutch to verify proper operation. 
Did you find and correct the condition?

System 

OK

Go to Step 2

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.

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

Fig. 6: Left & Right Engine Block Coolant Drain Hole Plugs 
Courtesy of GENERAL MOTORS CORP. 

7. If a complete engine block drain is required, remove the left and right engine block coolant drain plugs.  

8. Remove the engine block coolant heater, if equipped. Refer to Coolant Heater Replacement .  

9. Inspect the coolant.  

10. Follow the appropriate procedure based on the condition of the coolant. 

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Normal in appearance-Follow the filling procedure.  

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Discolored-Follow the flush procedure. Refer to Flushing .  

Filling Procedure 

1. Install the lower radiator hose to the radiator.  

2. Using the J 38185 reposition the lower radiator hose clamp. See Special Tools and Equipment . 

NOTE:

The procedure below must be followed. Improper coolant level could 
result in a low or high coolant level condition, causing engine damage.

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

3. If the left and right engine block coolant drain plugs were removed, perform the following. 

1. Apply pipe sealer to the drain plugs. 

2. Install the drain plugs. 

Tighten: Tighten the drain plugs to 60 N.m (44 lb ft). 

4. Install the engine block coolant heater, if equipped. Refer to Coolant Heater Replacement .  

5. Lower the vehicle.  

6. Open the cooling system bleeder screws. 

7. Slowly fill the cooling system with a 50/50 coolant mixture. Refer to Capacities - Approximate Fluid in 

Maintenance and Lubrication.  

8. Close the cooling system bleeder screws.  

9. Install the coolant pressure cap.  

10. Start the engine.  

11. Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.  

12. Allow the engine to idle for 3 minutes.  

13. Shut the engine OFF.  

14. Allow the engine to cool.  

15. Top off the coolant as necessary.  

16. Inspect the concentration of the engine coolant using the J 26568 . See Special Tools and Equipment .  

17. Rinse away any excess coolant from the engine and the engine compartment.  

FLUSHING 

NOTE:

Refer to Fastener Notice in Cautions and Notices.

IMPORTANT: Use a 50/50 mixture of DEX-COOL antifreeze and clean, drinkable water.

IMPORTANT:

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Do not use a chemical flush.  

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Store used coolant in the proper manner, such as in a used engine 
coolant holding tank. Do not pour used coolant down a drain. Ethylene 
glycol antifreeze is a very toxic chemical. Do not dispose of coolant into 
the sewer system or ground water. This is illegal and ecologically 
unsound.  

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Various methods and equipment can be used to flush the cooling system. 
If special equipment is used (such as a back flusher) follow the 
manufacturer's instructions. However, always remove the thermostat 
before back flushing the system.  

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2