Chevrolet Silverado / GMC Sierra. Service manual — part 1611

Fig. 3: View Of Thermostat Test Procedure Using Glycol
Courtesy of GENERAL MOTORS CORP.

1. Completely submerge the thermostat in the glycol solution. The solution should be 11°C

(22°F) above the temperature indicated on the thermostat valve.

2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.

In order to inspect if the thermostat valve is closing properly, perform the following test:

2008 Chevrolet Silverado 1500

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

1. Completely submerge the thermostat in a glycol solution. The solution should be 6°C (10°F)

below the temperature indicated on the thermostat valve.

2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close

completely.

COOLANT HEATER INOPERATIVE (GASOLINE)

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The optional coolant heater operates using 110 volt AC external power and is designed to warm
the coolant in the engine block area for improved starting in very cold weather. There is an
internal thermal switch in the power cord that prevents operation above -18°C (0°F). The coolant
heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped
with a detachable AC power cord. A weather shield on the cord is provided to protect the plug
when not in use.

Reference Information

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Circuit/System Testing

1. Test the engine coolant heater for an open or short to ground.

If open or shorted, replace the heater.

2. If the heater tests normal, replace the coolant heater power cord.

IMPORTANT: The power supply cord will read open due to an internal thermal

switch if the ambient temperature is above -18°C (0 °F).

2008 Chevrolet Silverado 1500

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

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Coolant Heater Replacement (LH6, LY2, LMG, LY5, and LY6) or Coolant Heater
Replacement (L76, L92)

Coolant Heater Cord Replacement (L76 and L92) or Coolant Heater Cord
Replacement (LH6, LMG, LY2 and LY5) or Coolant Heater Cord Replacement
(LY6)

ENGINE FAILS TO REACH NORMAL OPERATING TEMPERATURE

PRESSURE CAP TESTING

Step

Action

Yes

No

1

Did you review the Symptoms - Engine Cooling
diagnostic information and perform the
necessary inspections?

Go to Step 2

Go to Symptoms
- Engine
Cooling

2

Verify that the engine does not reach normal
operating temperature.
Does the engine reach normal operating
temperature?

System OK

Go to Step 3

3

Inspect the coolant level.
Is the coolant level below the add mark?

Go to Step 4

Go to Step 5

4

1. Add coolant as necessary.

2. Perform a cooling system pressure test.

Does the cooling system hold pressure?

System OK

Go to Step 5

5

Inspect for a stuck open, missing, or incorrect
thermostat. Refer to Thermostat Diagnosis.
Is the thermostat operating properly?

System OK

Go to Step 6

6

Install the correct replacement thermostat. Refer
to Engine Coolant Thermostat Housing
Replacement (LY2, LH6, LY5, LMG, LY6).
Is the repair complete?

Go to Step 7

-

7

Run the engine in order to verify the repair.
Does the engine fail to reach normal operating
temperature?

-

System OK

2008 Chevrolet Silverado 1500

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

Tools required

J 24460-01 Cooling System Pressure Tester

J 42401 Radiator Cap / Surge Tank Test Adapter

Pressure Cap Testing

1. Remove the pressure cap.

2. Wash the pressure cap sealing surface with water.

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.

2008 Chevrolet Silverado 1500

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