GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Check for an incorrect or faulty surge tank cap.

Is the surge tank cap incorrect or faulty?

--

Go to Step 2

Go to Step 3

2

Replace the surge tank cap.

Is there still a coolant loss?

103 kPa (15 psi)

Go to Step 3

System OK

3

  1. Ensure that the cooling system is full.
  2. Pressure test the cooling system.
  3. While the cooling system is pressurized, inspect for any external coolant leaks.
  4. Repair or replace the leaking components as necessary.

Is there still a coolant loss?

--

Go to Step 4

System OK

4

Check the heater core for leakage.

Is the heater core leaking?

--

Go to Step 5

Go to Step 6

5

Replace the heater core. Refer to Heater Core Replacement in Heating, Ventilation and Air Conditioning.

Is there still a loss of coolant?

--

Go to Step 6

System OK

6

Start the engine and inspect.

Is there excessive white smoke from the exhaust and/or does the engine idle rough?

--

Go to Step 10

Go to Step 7

7

Road test the vehicle and allow the engine to reach full operating temperature.

Does the engine overheat?

--

Go to Engine Overheating

Go to Step 8

8

Remove the oil level indicator stick and inspect.

Is there engine coolant or a creamy/milky substance on the engine oil level indicator?

--

Go to Step 9

Go to Step 1

9

Important: Ensure that the cause of the creamy or milky substance is not caused by short drive cycles or a faulty thermostat. Either of these conditions will cause creamy or milky deposits to form in the engine oil because the engine cannot reach full operating temperature in order to dissipate the condensation/moisture.

Does the engine reach full operating temperature during all of the vehicle drive cycles?

--

Go to Step 10

Go to Engine Fails To Reach Normal Operating Temperature

10

The probable cause of the coolant loss is an engine internal coolant leak. If the spark plug electrodes or the porcelain surrounding the spark plug electrodes exhibit signs of coolant, replace the applicable cylinder heads or cylinder head gaskets.

Did you complete the repair?

--

Go to Step 11

 

11

  1. Ensure that the cooling system is full. Refer to Cooling System Draining and Filling .
  2. Operate the system in order to verify the repair.

Is there still a coolant loss?

--

Go to Step 1

System OK