Hummer H2. Manual - part 1699

Fig. 19: Identifying J 21867 (Pressure Gauge) & J 42907 (Oil Pressure Testing Tool) 
Courtesy of GENERAL MOTORS CORP. 

1. With the vehicle on a level surface, run the vehicle for a few minutes. Allow adequate drain down time, 

2-3 minutes, and measure the oil level.  

2. If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full 

on the oil level indicator.  

3. Run the engine briefly, 10-15 seconds, and verify low or no oil pressure on the vehicle gauge or light.  

4. Listen for a noisy valve train or a knocking noise.  

5. Inspect for the following conditions: 

z

Oil diluted by water or glycol anti freeze  

z

Foamy oil  

6. Remove the oil filter and install the J 42907 . 

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

7. Install J 21867 or equivalent to the J 42907 . See Special Tools and Equipment .  

8. Run the engine and measure the engine oil pressure.  

9. Compare the readings to Engine Mechanical Specifications .  

10. If the engine oil pressure is below specifications, inspect the engine for one or more of the following 

conditions: 

z

Oil pump worn or dirty 

Refer to Oil Pump Cleaning and Inspection . 

z

Oil pump-to-engine block bolts loose 

Refer to Oil Pump, Pump Screen and Deflector Installation . 

z

Oil pump screen loose, plugged, or damaged  

z

Oil pump screen O-ring seal missing or damaged  

z

Malfunctioning oil pump pressure relief valve  

z

Excessive bearing clearance  

z

Cracked, porous, or restricted oil galleries  

z

Oil gallery plugs missing or incorrectly installed 

Refer to Engine Block Plug Installation . 

z

Broken valve lifters 

Repair as necessary. 

11. If the oil pressure reading on the J 21867 or equivalent is within specifications, inspect for the following 

conditions:. See Special Tools and Equipment . 

z

Plugged or incorrect oil filter and/or malfunctioning oil bypass valve  

z

Malfunctioning oil pressure gauge or sensor 

Repair as necessary. 

OIL LEAK DIAGNOSIS 

Oil Leak Diagnosis 

Step

Action

Yes

No

IMPORTANT:

You can repair most fluid leaks by first visually locating the leak, repairing or replacing the 
component, or by resealing the gasket surface. Once the leak is identified, determine the cause of 
the leak. Repair the cause of the leak as well as the leak itself.

1. Operate the vehicle until it reaches normal operating temperature.  

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

1

2. Park the vehicle on a level surface, over a large sheet of paper or other 

clean surface.  

3. Wait 15 minutes.  

4. Check for drippings.  

Are drippings present?

Go to 

Step 2

System 

OK

2

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 3

3

1. Visually inspect the suspected area. Use a small mirror to assist in looking 

at hard to see areas.  

2. Check for leaks at the following locations: 

z

Sealing surfaces  

z

Fittings  

z

Cracked or damaged components  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 4

4

1. Completely clean the entire engine and surrounding components.  

2. Operate the vehicle for several kilometers - miles at normal operating 

temperature and at varying speeds.  

3. Park the vehicle on a level surface, over a large sheet of paper or other 

clean surface.  

4. Wait 15 minutes.  

5. Identify the type of fluid, and the approximate location of the leak.  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 5

5

1. Visually inspect the suspected area. Use a small mirror to assist in looking 

at hard to see areas.  

2. Check for leaks at the following locations: 

z

Sealing surfaces  

z

Fittings  

z

Cracked or damaged components  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 6

6

1. Completely clean the entire engine and surrounding components.  

2. Apply an aerosol-type powder, baby powder, foot powder, etc., to the 

suspected area.  

3. Operate the vehicle for several kilometers (miles) at normal operating 

temperature and at varying speeds.  

4. Identify the type of fluid, and the approximate location of the leak, from 

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

  

the discolorations in the powder surface.  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 7

7

1. Visually inspect the suspected area. Use a small mirror to assist in looking 

at hard to see areas.  

2. Check for leaks at the following locations: 

z

Sealing surfaces  

z

Fittings  

z

Cracked or damaged components  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 8

8

Use J 28428-E High Intensity Black Light Kit in order to identify the type of 
fluid, and the approximate location of the leak. Refer to the manufacturer's 
instructions when using the tool. See Special Tools and Equipment . 
Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

Go to 

Step 9

9

1. Visually inspect the suspected area. Use a small mirror to assist in looking 

at hard to see areas.  

2. Check for leaks at the following locations: 

z

Sealing surfaces  

z

Fittings  

z

Cracked or damaged components  

Can you identify the type of fluid and the approximate location of the leak?

Go to 

Step 

10

System 

OK

10

1. Inspect the engine for mechanical damage. Special attention should be 

shown to the following areas: 

z

Higher than recommended fluid levels  

z

Higher than recommended fluid pressures  

z

Plugged or malfunctioning fluid filters or pressure bypass valves  

z

Plugged or malfunctioning engine ventilation system  

z

Improperly tightened or damaged fasteners  

z

Cracked or porous components  

z

Improper sealants or gaskets where required  

z

Improper sealant or gasket installation  

z

Damaged or worn gaskets or seals  

z

Damaged or worn sealing surfaces  

2. Inspect the engine for customer modifications.  

Is there mechanical damage, or customer modifications to the engine?

Go to 

Step 

11

System 

OK

11

Repair or replace all damaged or modified components. 
Does the engine still leak oil?

Go to 

Step 1

System 

OK

 

2004 Hummer H2 

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2