Chevrolet Silverado / GMC Sierra. Manual — part 1612

Fig. 4: Pressure Testing Radiator Cap
Courtesy of GENERAL MOTORS CORP.

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

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.

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

J 42401 Radiator Cap/ Surge Tank Test Adapter

Testing

IMPORTANT: Lubricate J-42401 and pressure cap o-rings with coolant and

press cap to seat o-ring on J-42401 before turning to engage
threads.

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

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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.

Fig. 5: Applying Pressure To Cooling System Using J 42401
Courtesy of GENERAL MOTORS CORP.

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.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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

Do not exceed the pressure cap rating.

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

Observe the gage for any pressure loss.

6. Repair any leaks as required.

FAN CLUTCH DIAGNOSIS

Step

Action

Yes

No

1

Were you sent here from Symptoms or another
diagnostic table?

Go to Step 2

Go to Symptoms

- Engine

Cooling

2

Is there 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.

Slight silicone leakage may not effect the
fan clutch engagement.

Excess leakage will prevent the fan clutch
from engaging.

Is the silicone fluid leakage excessive?

Go to Step 14

Go to Step 7

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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.
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

-

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.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado