GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Inspect for a loss of system pressure.

Refer to Cooling System Leak Testing .

Is there a loss of system pressure?

--

Go to Step 2

Go to Step 3

2

Inspect and repair any faulty hose connections.

Does the engine still overheat?

--

Go to Step 3

System OK

3

Inspect for low coolant protection (-37°C/-34°F). Refer to Coolant Concentration Testing .

Is low coolant protection persent? (-37°C/-34°F)?

--

Go to Step  4

Go to Step 5

4

Replace the coolant. Refer to Cooling System Draining and Filling .

Does the engine still overheat?

--

Go to Step 5

System OK

5

Inspect the drive belt for excessive wear or low tension.

Is the drive belt worn or is the tension too low?

--

Go to Step 6

Go to Step 7

6

Replace the drive belt. Refer to Drive Belt Replacement in Engine Mechanical.

Does the engine still overheat?

--

Go to Step 7

System OK

7

Inspect the water pump.

Is the water pump inoperative?

--

Go to Step 8

Go to Step 9

8

Replace the water pump.

Does the engine still overheat?

--

Go to Step 9

System OK

9

Inspect the radiator fins for obstruction.

Are the radiator fins obstructed?

--

Go to Step 10

Go to Step 11

10

Inspect and clean the radiator.

Does the engine still overheat?

--

Go to Step 11

System OK

11

Inspect the cooling system passage for obstruction.

Is the cooling system passage blocked?

--

Go to Step 12

Go to Step 13

12

Inspect and flush the system.

Refer to Flushing .

Does the engine still overheat?

--

Go to Step 13

System OK

13

Insepct the fan clutch.

Is the fan clutch inoperative?

--

Go to Step 14

Go to Step 15

14

Replace the fan clutch. Refer to the appropriate procedure:

    •  Fan Clutch Replacement
    •  Fan Clutch Replacement

Does the engine still overheat?

--

Go to Step 15

System OK

15

Inspect for a stuck thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?

--

Go to Step 16

Go to Step 17

16

Replace the thermostat.

Does the engine still overheat?

--

Go to Step 17

System OK

17

The following factors may cause the engine to overheat:

    • A heavy vehicle payload
    • The A/C system
    • Excess engine oil
    • Restricted air flow through the radiator
    • Extreme air temperature

Correct or repair as necessary.

Does the engine still overheat?

--

--

System OK