GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Inspect the following conditions:

    • The level of the coolant
    • The mixture of the coolant

Is the coolant mixed properly and at the proper level?

Go to Step 3

Go to Step 2

2

Add the coolant.

Does the engine still overheat?

Go to Step 3

System OK

3

Inspect the generator/coolant pump drive belt.

Is the generator/coolant pump drive belt loose or missing?

Go to Step 4

Go to Step 5

4

Adjust or replace the belt.

Does the engine still overheat?

Go to Step 5

System OK

5

Inspect the front of the radiator for the following items:

    • Dirt
    • Leaves
    • Insects

Is the front of the radiator dirty?

Go to Step 6

Go to Step 7

6

Clean the front of the radiator.

Does the engine still overheat?

Go to Step 7

System OK

7

Inspect the following components for leaks:

    • The hoses
    • The coolant pump
    • The heater
    • The thermostat housing
    • The radiator
    • The head gasket

Is leakage present?

Go to Step 8

Go to Step 9

8

Repair the leaks as necessary.

Does the engine still overheat?

Go to Step 9

System OK

9

Inspect the thermostat.

Is the thermostat faulty?

Go to Step 10

Go to Step 11

10

Replace the thermostat.

Does the engine still overheat?

Go to Step 11

System OK

11

Inspect the cylinder head torque.

Is the cylinder head torque correct?

Go to Step 13

Go to Step 12

12

  1. Re-tighten the cylinder head bolts to specification.
  2. Replace the cylinder head gasket if required.

Does the engine still overheat?

Go to Step 13

System OK

13

Inspect the intake manifold.

Is the intake manifold leaking?

Go to Step 14

Go to Step 15

14

Complete the following actions as necessary in order to correct the leak:

    • Repair the intake manifold.
    • Replace the components.

Does the engine still overheat?

Go to Step 15

System OK

15

Inspect the cylinder head gasket.

Is the cylinder head gasket leaking?

Go to Step 16

Go to Step 17

16

Repair or replace the components as necessary in order to correct the leak.

Does the engine still overheat?

Go to Step 17

System OK

17

Inspect the cylinder block plug.

Is the cylinder block plug leaking?

Go to Step 18

Go to Step 19

18

Repair or replace the components as necessary in order to correct the leak.

Does the engine still overheat?

Go to Step 19

System OK

19

Inspect the heater core.

Is the heater core leaking?

Go to Step 20

Go to Step 21

20

Repair or replace the components as necessary in order to correct the leak.

Does the engine still overheat?

Go to Step 21

System OK

21

Inspect the coolant valve, if equipped.

Is the coolant valve leaking?

Go to Step 22

--

22

Repair or replace the components as necessary in order to correct the leak.

Does the engine still overheat?

--

System OK