Chevrolet Silverado / GMC Sierra. Service manual — part 407

OIL PRESSURE DIAGNOSIS AND TESTING

Allow adequate time for the rings to seat.

Replace worn piston rings as necessary.

Piston and rings improperly installed or improperly fit to
the cylinder bore

Step

Action

Yes

No

DEFINITION: Low or no engine oil pressure indicates a potentially serious condition with
all of the engine mechanical components. Once the cause of the low or no oil pressure
condition has been identified, repair all collateral damage to the engine mechanical
components as well as the initial cause of the condition.

1

Check engine oil level. Use only the GM service
parts brand and recommended grade of engine
oil specified for the vehicle.
Is the engine oil level between ADD and FULL
on the oil level indicator?

Go to Step 2

-

2

1. Operate vehicle until engine reaches normal

operating temperature. Refer to Engine
Mechanical Specifications.

2. Park vehicle on a level surface.

3. Wait 15 minutes.

4. Check engine oil level. Use only the GM

service parts brand and recommended
grade of engine oil specified for the
vehicle.

Is the engine oil level between ADD and FULL
on the oil level indicator?

Go to Step 3

-

3

Operate the engine and measure the engine oil
pressure with the vehicle gage or light. Refer to
Engine Mechanical Specifications.
Is engine oil pressure within specification?

System OK

Go to Step 4

1. Remove the oil pressure sender or engine

block oil gallery plug.

2. Install a mechanical oil pressure gage.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

4

3. Operate the engine and measure the engine

oil pressure with the mechanical oil
pressure gage. Refer to Engine
Mechanical Specifications.

Is engine oil pressure within specification?

System OK

Go to Step 5

5

Change the engine oil and filter.

Use only the GM service parts brand and
recommended grade of engine oil specified
for the vehicle. Refer to Owners' Manual.

Use only the GM service parts brand and
recommended type of engine oil filter
specified for the vehicle. Refer to Owners'
Manual.

Operate the engine and measure the engine oil
pressure with the mechanical oil pressure gage.
Refer to Engine Mechanical Specifications.
Is engine oil pressure within specification?

System OK

Go to Step 6

6

1. Inspect the engine for mechanical damage.

Special interest should be shown to the
following areas:

Malfunctioning oil bypass valve

Oil pump worn or dirty

Oil pump-to-engine block bolts loose

Oil pump O-ring damaged or missing

Oil pump to oil pump pipe and screen
assembly gasket missing or damaged

Oil pump pipe and screen assembly
restrictions or damaged

Oil pump driven gear damaged or
loose

Oil pump drive gear damaged

Oil cooler restrictions

Oil cooler O-rings damaged or

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

OIL LEAK DIAGNOSIS

missing

Excessive bearing clearances

Cracked, porous or restricted oil
galleries

Oil gallery plugs missing or
incorrectly installed

Damaged or missing oil spray cooling
nozzles

2. Inspect the engine for customer

modifications.

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

Go to Step 7

Go to Step 1

7

Repair or replace all damaged or modified
components.
Is the repair complete?

Go to Step 1

-

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

1. Operate the vehicle until it reaches normal

operating temperature.

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 7

Go to Step 3

1. Visually inspect the suspected area. Use a

small mirror to assist in looking at hard to
see areas.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

3

2. Check for leaks at the following locations:

Sealing surfaces

Fittings

Cracked or damaged components

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

Go to Step 7

Go to Step 4

4

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 the
discolorations in the powder surface.

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

Go to Step 7

Go to Step 5

5

Use J 28428-E 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.
Can you identify the type of fluid and the
approximate location of the leak?

Go to Step 7

Go to Step 6

6

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:

Sealing surfaces

Fittings

Cracked or damaged components

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

Go to Step 7

System OK

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado