Hummer H2. Manual - part 1385

Fig. 4: J 24460-01 & J 42401 
Courtesy of GENERAL MOTORS CORP. 

3. Use the J 24460-01 (1) with J 42401 (2) in order to test the pressure cap. See Special Tools and 

Equipment .  

4. Test the pressure cap for the following conditions: 

z

Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap. See Special 
Tools and Equipment .  

z

Maintain the rated pressure for at least 10 seconds. 

Note the rate of pressure loss. 

5. Replace the pressure cap under the following conditions: 

z

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

z

The pressure cap does not hold the rated pressure.  

COOLING SYSTEM LEAK TESTING 

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

Tools Required 

z

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

z

J 42401 Radiator Cap/Surge Tank Test Adapter. See Special Tools and Equipment .  

1. Remove the pressure cap.  

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

3. Wash the pressure cap mating surface with water. 

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.

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

Fig. 5: Using J 24460-01 With J42401 To Apply Pressure To Cooling System 
Courtesy of GENERAL MOTORS CORP. 

4. Use the J 24460-01 with the J 42401 in order to apply pressure to the cooling system. See Special Tools 

and Equipment . 

Do not exceed the pressure cap rating. 

5. The cooling system should hold the rated pressure for at least 2 minutes. 

Observe the gauge for any pressure loss. 

6. Repair any leaks as required.  

FAN CLUTCH DIAGNOSIS 

Fan Clutch Diagnosis 

Step

Action

Yes

No

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2

  

Definition: Testing the engagement and disengagement of the fan clutch.

1

Were you sent here from Symptoms or another diagnostic table?

Go to 

Step 2

Go to Symptoms - 

Engine Cooling

2

Do you notice excessive fan air noise?

Go to 

Step 3

Go to Step 4

3

Fan air noise is normal during cold engine start up. 
Does the fan noise go away at normal engine operating 
temperature?

Go to 

Step 13

Go to Step 4

4

Rotate the fan clutch.Does the fan clutch rotate?

IMPORTANT:

The engine must be turned OFF and the engine temperature 
should be cold.

Go to 

Step 5

Go to Step 14

5

Visually inspect the fan blades for cracks, looseness or damage. 
Are the fan blades in good condition?

Go to 

Step 6

Go to Step 15

6

Visually inspect the fan clutch for signs of silicone leakage. 

z

Slight silicone leakage may not effect the fan clutch 
engagement.  

z

Excess leakage will prevent the fan clutch from engaging.  

 
Is the silicone fluid leakage excessive?

Go to 

Step 14

Go to Step 7

7

Inspect the fan clutch for proper installation. 

1. Move the fan blade back and forth in a lateral motion.  

2. Inspect for fan blade to fan clutch movement.  

 
Is the fan blade loose at the fan clutch?

Go to 

Step 10

Go to Step 8

8

Inspect the fan clutch for wear. 

1. Move the fan blade back and forth in a lateral motion. 

2. Inspect for fan clutch lateral movement.  

 
Is the fan clutch lateral movement excessive?

IMPORTANT:

Approximately 6.5 mm (1/4 in) movement at the tip of the 
fan blade is normal.

Go to 

Step 14

Go to Step 9

9

The fan clutch should have more turning resistance when the engine 
is at or above normal operating temperature. 

 

2004 Hummer H2 

2004 ENGINE Engine Cooling - Hummer H2