GM Service Manual Online
For 1990-2009 cars only

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?

Go to Step 6

Go to Step 8

6

Is the vehicle equipped with a 6.6 L diesel engine?

Go to Step 7

Go to Step 8

7

Inspect for a faulty turbocharger coolant bypass valve

Is the turbocharger coolant bypass valve functioning properly?

--

Go to Step 9

8

Install the correct replacement thermostat. Refer to Engine Coolant Thermostat Replacement .

Is the repair complete?

Go to Step 10

--

9

Install a new turbocharger coolant bypass valve. Refer to Turbocharger Coolant Bypass Valve Replacement .

Is the repair complete?

Go to Step 10

--

10

Run the engine in order to verify the repair.

Does the engine fail to reach normal operating temperature?

--

System OK