GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Check the level of the coolant in the radiator surge tank.

Is the coolant in the surge tank at the proper level?

--

Go to Step 3

Go to Step 2

2

Add engine coolant as necessary. Refer to Cooling System Draining and Filling .

Does the engine still fail to reach normal operating temperature?

--

Go to Step 3

System OK

3

Check if the thermostat bypass valve is stuck open.

Is the thermostat bypass valve stuck in the open position?

--

Go to Step 4

Go to Step 5

4

If necessary replace the bypass valve.

Does the engine still fail to reach normal operating temperature?

--

Go to Step 5

System OK

5

Check to see if the correct type of thermostat was installed, or if the thermostat sticks (or is stuck) in the open position. Refer to Thermostat Diagnosis .

Was the incorrect thermostat installed or does the thermostat stick, or is the thermostat stuck, in the open position?

--

Go to Step 6

System OK

6

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine still fail to reach normal operating temperature?

--

--

System OK