1

Inspect the coolant level.

Is the coolant level low?

Go to Step 12

Go to Step 2

Inspect the exhaust system for the following conditions:

Did you find and correct the condition?

Go to Step 23

Go to Step 3

Inspect for a loose drive belt.

Is the drive belt loose?

Go to Step 4

Go to Step 5

Replace the drive belt. Refer to the appropriate procedure:

Was the repair complete?

Go to Step 23

--

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

Is the repair complete?

Go to Step 23

Go to Step 6

1. Inspect for obstructed radiator air flow.
2. If equipped with a 6.6L diesel, also inspect for an obstructed charged air cooler or debris between the radiator and air cooler.

Is the radiator air flow obstructed?

Go to Step 7

Go to Step 8

Clean the radiator. Refer to Radiator Cleaning .

Was the repair complete?

Go to Step 23

--

Inspect for an inoperative fan clutch. Refer to Fan Clutch Diagnosis .

Is the fan clutch operating correctly?

Go to Step 10

Go to Step 9

Replace the fan clutch. Refer to Fan Clutch Replacement .

Was the repair complete?

Go to Step 23

--

Inspect the thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?

Go to Step 11

Go to Step 16

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Was the repair complete?

Go to Step 23

--

1. Fill the coolant to the specified level.
2. Perform a pressure test on the cooling system.
3. Inspect for external coolant leaks.

Are there any external leaks?

Go to Step 22

Go to Step 13

Perform a pressure test on the radiator cap.

Does the radiator cap hold pressure?

Go to Step 15

Go to Step 14

Replace the radiator cap.

Was the repair complete?

Go to Step 23

--

Inspect for combustion chamber gases leaking in the cooling system.

Are bubbles present in the coolant?

Go to Step 20

Go to Step 16

Inspect for a inoperative water pump.

Is the water pump inoperative?

Go to Step 17

Go to Step 18

Replace the water pump. Refer to Water Pump Replacement .

Was the repair complete?

Go to Step 23

--

Inspect for a blockage in the engine block coolant passages.

Are the engine block coolant passages blocked?

Go to Step 19

--

Perform the cooling system flush. Refer to Flushing .

Was the repair complete?

Go to Step 23

--

Check the engine oil.

Is the engine oil foamy and/or milky?

Go to Step 21

--

1. Remove the cylinder head. Refer to the appropriate procedure:

•	Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side for the 4.3L engine

•	Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side for the 4.8L, 5.3L and 6.0L engine

•	Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side for the 6.6L (LLY) engine

•	Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side for the 8.1L engine

2. If equipped with a 8.1L engine, inspect the head gasket for correct installation. Refer to Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side for the 8.1L engine
3. Inspect the cylinder head and block for cracks.

Was a damaged/faulty component found?

Go to Step 22

--

Replace and/or repair the component as necessary.

Was the repair complete?

Go to Step 23

--

1. Fill the cooling system to the proper level, if necessary.
2. Operate the engine.

Does the engine overheat?

Go to Step 2

System OK