GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

DEFINITION:

    • Engine coolant temperature gauge pointer is in red area
    • Engine coolant overflowing from the coolant reservoir
    • Hissing, rumble, steam, or power loss

1

  1. Allow the engine to cool.
  2. Check the coolant level in the coolant recovery reservoir.

Is the coolant in the reservoir at the proper level?

--

Go to Step 3

Go to Step 2

2

Add coolant to the coolant reservoir. Use the proper coolant. Refer to Fluid and Lubricant Recommendations in Maintenance and Lubrication.

Is the repair complete?

--

Go to Step 26

--

3

Inspect the vehicle for aftermarket devices that may be blocking airflow to the radiator.

Are there any aftermarket devices that are blocking the airflow to the radiator?

--

Go to Step 4

Go to Step 5

4

Remove the obstruction.

Is the repair complete?

--

Go to Step 26

--

5

Consult with the owner as to if the vehicle has been operated under any of the following conditions:

    • Excessive vehicle payload
    • Continuous use of the A/C system while:
       - Towing
       - Driving in stop and go traffic
    • Extreme air temperatures

Has the vehicle been driven under any of the above conditions?

--

Go to Step 6

Go to Step 7

6

Advise the owner about proper driving techniques.

Is this action complete?

--

Go to Step 26

--

7

Check the engine oil level.

Is the engine oil level excessive?

--

Go to Step 8

Go to Step 9

8

Remove the excess engine oil.

Is the repair complete?

--

Go to Step 26

--

9

Check the radiator for the following conditions:

    • Obstructed cooling area around the radiator
    • Plugged radiator fins
    • Bent radiator fins

Are the any obstructed, plugged or bent radiator fins?

--

Go to Step 10

Go to Step 11

10

Clean the radiator surface as necessary. Refer to Drive Belt Replacement .

Is the repair complete?

--

Go to Step 26

--

11

Check the drive belt for the following conditions:

    • Looseness
    • Cracks
    • Glazing

Does any of the above apply?

--

Go to Step 12

Go to Step 13

12

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

Is the repair complete?

--

Go to Step 26

--

13

Pressure test the cooling system.

Is the cooling system holding pressure?

103 kPa (15 psi)

Go to Step 14

Go to Loss of Coolant

14

Check the radiator hoses for collapsed or restricted condition.

Are any of the radiator hoses collapsed or restricted?

--

Go to Step 15

Go to Step 16

15

Replace the hoses as necessary. Refer to Radiator Inlet Hose Replacement or Radiator Outlet Hose Replacement .

Is the repair complete?

--

Go to Step 26

--

16

Check the thermostat for proper operation. Refer to Thermostat Diagnosis .

Is the thermostat operating normally?

--

Go to Step 18

Go to Step 17

17

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Is the repair complete?

--

Go to Step 26

--

18

Check for a clogged radiator coolant passages. Refer to Flushing .

Are the radiator coolant passages clogged?

--

Go to Step 19

Go to Step 20

19

Repair or replace the radiator as necessary.

Is the repair complete?

--

Go to Step 26

--

20

Check for a blockage in the engine block coolant passages.

Are the engine block cooling passages normal?

--

Go to Step 22

Go to Step 21

21

Clean the engine cooling passages as necessary.

Is the repair complete?

--

Go to Step 26

--

22

Check the radiator fan blade clutch. Refer to Fan Replacement .

Is the fan blade clutch operating normally?

--

Go to Step 24

Go to Step 23

23

Replace the fan blade clutch. Refer to Fan Replacement .

Is the repair complete?

--

Go to Step 26

--

24

Check the coolant pump for a low pumping volume.

Is the pumping volume of the pump normal?

--

System OK

Go to Step 25

25

Replace the coolant pump. Refer to Water Pump Replacement .

Is the repair complete?

--

Go to Step 26

--

26

  1. Start the engine.
  2. Run the engine while observing the engine coolant temperature gauge.

Does the engine still overheat?

--

Go to Step 1

System OK