GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value

Yes

No

DEFINITION: The engine temperature lamp comes on and stays on, or the temperature gauge shows hot, or coolant overflows from the surge tank onto the ground while the engine is running.

1

Check for a loss of coolant.

Is there a loss of coolant?

--

Go to Step 2

Go to Step 3

2

Fill the system to the specified level. Refer to Cooling System Draining and Filling .

Does the engine still overheat?

--

Go to Step 3

System OK

3

Check for a missing or damaged radiator upper air deflector, baffle, or center air deflector.

Are there any missing or damaged deflectors or baffles?

--

Go to Step 4

Go to Step 5

4

Repair or replace any deflectors or baffles as necessary.

Does the engine still overheat?

--

Go to Step 5

System OK

5

Check the coolant concentration. Refer to Coolant Concentration Testing .

Is the coolant concentration adequate?

--

Go to Step 7

Go to Step 6

6

Correct the coolant concentration as necessary. Refer to Flushing .

Does the engine still overheat?

--

Go to Step 7

System OK

7

Check for a loss of cooling system pressure.

Does the cooling system maintain the correct pressure?

--

Go to Step 9

Go to Step 8

8

Pressure test the cooling system. Correct as necessary. Refer to Cooling System Leak Testing .

Does the engine still overheat?

103 kPa (15 psi)

Go to Step 9

System OK

9

Check for a pinched or kinked radiator surge tank hose.

Is the surge tank hose kinked or damaged?

--

Go to Step 10

Go to Step 11

10

Reroute or replace the hose as necessary. Refer to Radiator Surge Tank .

Does the engine still overheat

--

Go to Step 11

System OK

11

  1. Check the drive belt tension. Refer to Drive Belt Diagnosis .
  2. Check the tensioner.

Is the tensioner working properly?

--

Go to Step 13

Go to Step 12

12

Replace the tensioner as necessary. Refer to Accessory Drive Belt Tensioner Replacement in Engine Mechanical.

Does the engine still overheat?

--

Go to Step 13

System OK

13

Check for an obstructed radiator air flow or bent fins.

Are any radiator fins bent or is air flow to the radiator being obstructed?

--

Go to Step 15

Go to Step 14

14

Check for a blockage in the cooling system passages.

Are the cooling system passages blocked?

--

Go to Step 16

Go to Step 17

15

Remove or relocate add on parts that block air flow to the radiator. Refer to Cooling System .

Does the engine still overheat?

--

Go to Step 17

System OK

16

  1. Drain the coolant. Refer to Cooling System Draining and Filling .
  2. Flush the cooling system. Refer to Flushing .
  3. Repair as necessary.

Does the engine still overheat?

--

Go to Step 17

System OK

17

Check for an inoperative cooling fan. Refer to Electrical Diagnosis.

Are any cooling fans inoperative?

--

Go to Step 18

Go to Step 19

18

Repair or replace the cooling fan as necessary. Refer to Electrical Diagnosis.

Does the engine still overheat?

--

Go to Step 19

System OK

19

Check if the thermostat is stuck in the closed position. Refer to Thermostat Diagnosis .

Is the thermostat sticking (or stuck) in the closed position?

--

Go to Step 20

Go to Step 21

20

Replace the thermostat as necessary. Refer to Engine Coolant Thermostat Replacement .

Does the engine still overheat?

--

Go to Step 21

System OK

21

Check for a faulty coolant pump.

Is the coolant pump faulty?

--

Go to Step 22

Go to Step 23

22

Replace the coolant pump as necessary. Refer to Water Pump Replacement .

Does the engine still overheat?

--

Go to Step 23

System OK

23

Check the radiator cooling capacity. Make sure the proper sized radiator is being used on the cooling system.

Is the correct sized radiator being used with the cooling system?

--

System OK

Go to Step 24

24

If necessary, install the correct radiator. Refer to Radiator Replacement .

Does the engine still overheat?

--

--

System OK