GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Inspect for a missing or damaged radiator upper or lower baffle and/or radiator air deflector.

Is the baffle and/or deflector missing or damaged?

Go to Step 8

Go to Step 2

2

Inspect for a loss of coolant.

Is there a loss of coolant?

Go to Step 3

Go to Step 4

3

Fill the system to the specified level. Refer to Loss of Coolant .

Does the engine overheat?

Go to Step 4

System OK

4

Inspect for low coolant protection.

Is the coolant to the correct concentration?

Go to Step 5

Go to Step 8

5

Inspect for a loss of cooling system pressure.

Is there a loss of system pressure?

Go to Step 8

Go to Step 6

6

Inspect for a faulty engine coolant temperature (ECT) sensor. Refer to DTC P0117 , DTC P0118 , or DTC P0125 in Engine Controls - 3.8L or DTC P0117 , DTC P0118 , or DTC P0125 in Engine Controls - 5.7L.

Is the sensor operating properly?

Go to Step 7

Go to Step 8

7

Inspect for a cracked coolant recovery reservoir or a leaking hose.

Is the coolant recovery reservoir cracked or is the hose leaking?

Go to Step 8

Go to Step 3

8

Repair or install new parts as necessary, then retest.

Does the engine overheat?

Go to Step 9

System OK

9

Inspect for incorrect drive belt tension.

Is the belt tension correct?

Go to Step 10

Go to Step 8

10

Remove the water pump. Refer to Water Pump Replacement . Inspect for a damaged water pump driveshaft.

Is the water pump driveshaft damaged or is the seal leaking?

Go to Step 8

Go to Step 11

11

Inspect for obstructed radiator air flow or bent radiator fins.

Is the radiator air flow obstructed?

Go to Step 8

Go to Step 12

12

Inspect for blocked cooling system passages.

Are the cooling system passages blocked?

Go to Step 8

Go to Step 13

13

Inspect for inoperative cooling fans. Refer to Cooling Fan Inoperative .

Are the cooling fans and the motors operating correctly?

Go to Step 14

Go to Step 8

14

Inspect the thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?

Go to Step 15

Go to Step 16

15

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine overheat?

Go to Step 16

System OK

16

Inspect the radiator cooling capacity.

Is the proper sized radiator being used on the vehicle?

Go to Step 3

Go to Step 17

17

Consult the current parts catalog and replace the radiator. Refer to Radiator Replacement .

Is the repair complete?

System OK

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