GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

DEFINITION: Hot light on, hissing, rumble, steam, or power loss.

1

Check the coolant level in the coolant recovery reservoir.

Is the coolant to the proper level?

--

Go to Step 3

Go to Step 2

2

  1. Add the proper coolant. Refer to

    Notice: Pure coolant can be added to raise the boiling point of the coolant, but too much will affect the freezing point. Do not use a solution stronger than 70 percent, as the freeze level rises rapidly after this point. Pure coolant will freeze at -22°C (-8°F).

    .
  2. Check for visual coolant leaks.

Are there any coolant leaks?

--

Go to Step 4

Go to Step 5

3

Check for a loose accessory drive belt.

Is the drive belt loose?

--

Go to Step 6

Go to Step 7

4

Repair any coolant leaks as necessary.

Does the engine still overheat?

--

Go to Step 3

System OK

5

  1. Pressure test the cooling system. Refer to Radiator Leak Testing .
  2. Check for coolant leaks.

Are there any coolant leaks?

--

Go to Step 4

Go to Step 3

6

Check the condition of the drive belt.

Does the engine still overheat?

--

Go to Step 7

System OK

7

Check the condition of the radiator hoses.

Are the hoses in good condition?

--

Go to Step 9

Go to Step 8

8

Replace the hose(s) as necessary. Refer to Radiator Hose Replacement .

Does the engine still overheat?

--

Go to Step 9

System OK

9

Check the temperature of the thermostat. Refer to Thermostat Diagnosis .

Is the temperature level of the thermostat normal?

--

Go to Step 11

Go to Step 10

10

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine still overheat?

--

Go to Step 11

System OK

11

Check for a clogged radiator. Refer to Radiator Diagnosis .

Are the radiator coolant passages normal?

--

Go to Step 12

--

12

Check for a blockage in the engine block coolant passages. Refer to Flushing .

Are the engine block cooling passages normal?

--

Go to Step 13

--

13

Check if there are any combustion chamber gases leaking into the cooling system.

Are there any bubbles present in the coolant?

--

Go to Step 14

Go to Step 15

14

Repair as necessary. Refer to Engine Mechanical.

Does the engine still overheat?

--

Go to Step 15

System OK

15

Check the coolant pump for a low pumping volume. Refer to Cooling System Diagnosis .

Is the pumping volume of the pump normal?

--

Go to Step 17

Go to Step 16

16

Replace the coolant pump.

    • For gasoline engines, refer to Water Pump Replacement .
    • For diesel engines, refer to Water Pump Replacement .

Does the engine still overheat?

--

Go to Step 17

System OK

17

Check the radiator fan blade clutch. Refer to Fan Clutch Diagnosis .

Is the fan blade clutch operating normally?

--

Go to Step 19

Go to Step 18

18

Replace the fan blade clutch. Refer to Fan Clutch Replacement .

Does the engine still overheat?

--

Go to Step 19

System OK

19

Other factors, such as the following, may be causing 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