GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Check for a loss of system pressure.

Is there a loss of system pressure?

--

Go to Step 2

Go to Step 3

2

Check the hoses for loose connections. Repair any loose connections.

Does the engine still overheat?

--

Go to Step 3

System OK

3

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

Is the coolant protection low?

--

Go to Step 4

Go to Step 5

4

Test solution. Correct low coolant protection. Refer to Coolant Concentration Testing .

Does the engine still overheat?

--

Go to Step 5

System OK

5

Check the water pump belt for low tension.

Is the water pump belt tension too low?

--

Go to Step 6

Go to Step 7

6

Replace the water pump belt tensioner.

Does the engine still overheat?

--

Go to Step 7

System OK

7

Check for an inoperative water pump.

Is the water pump inoperative?

--

Go to Step 8

Go to Step 9

8

Replace the water pump. Refer to Water Pump Replacement .

Does the engine still overheat?

--

Go to Step 9

System OK

9

Check for obstructed radiator fins.

Are the radiator fins obstructed?

--

Go to Step 10

Go to Step 11

10

Clean the radiator fins.

Does the engine still overheat?

--

Go to Step 11

System OK

11

Check for a blocked system passage.

Is the system passage blocked?

--

Go to Step 12

Go to Step 13

12

Flush the system and reroute or replace the hose.

Does the engine still overheat?

--

Go to Step 13

System OK

13

Check the water pump for damage to the belt.

Is the belt damaged?

--

Go to Step 14

Go to Step 15

14

Replace the accessory drive belt.

Does the engine still overheat?

--

Go to Step 15

System OK

15

Check for inoperative cooling fan.

Is the cooling fan inoperative?

Refer to electrical cooling fan diagnosis

--

Go to Step 16

Go to Step 17

16

Check and repair cooling fan.

Does the engine still overheat?

--

Go to Step 17

System OK

17

Check for restricted throttle body circuit flow.

Is the throttle body circuit flow restricted?

--

Go to Step 18

Go to Step 19

18

Inspect and clear the orifice and the associated hose.

Does the engine still overheat?

--

Go to Step 18

System OK

19

Check the thermostat to see if it is in a closed position.

Is the thermostat in a closed position?

--

Go to Step 20

--

20

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine still overheat?

--

--

System OK