1

Inspect the coolant level.

Is the coolant level low?

Go to Step 11

Go to Step 2

Inspect the exhaust system for the following conditions:

Did you find and correct the condition?

Go to Step 22

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 Drive Belt Replacement in Engine Mechanical -4.3L, Drive Belt Replacement - Accessory in Engine Mechanical - 4.8L, 5.3L and 6.0L, Drive Belt Replacement in Engine Mechanical - 6.6L or Drive Belt Replacement - Accessory in Engine Mechanical - 8.1L.

Was the repair complete?

Go to Step 22

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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 6

Go to Step 7

Clean the radiator. Refer to Radiator Cleaning .

Was the repair complete?

Go to Step 22

--

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

Is the fan clutch operating correctly?

Go to Step 9

Go to Step 8

Replace the fan clutch. Refer to Fan Clutch Replacement .

Was the repair complete?

Go to Step 22

--

Inspect the thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?

Go to Step 10

--

Replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Was the repair complete?

Go to Step 22

--

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 21

Go to Step 12

Perform a pressure test on the radiator cap.

Does the radiator cap hold pressure?

Go to Step 14

Go to Step 13

Replace the radiator cap.

Was the repair complete?

Go to Step 22

--

Inspect for combustion chamber gases leaking in the cooling system.

Are bubbles present in the coolant?

Go to Step 19

Go to Step 15

Inspect for a inoperative water pump.

Is the water pump inoperative?

Go to Step 16

Go to Step 17

Replace the water pump. Refer to Water Pump Replacement .

Was the repair complete?

Go to Step 22

--

Inspect for a blockage in the engine block coolant passages.

Are the engine block coolant passages blocked?

Go to Step 18

--

Perform the cooling system flush. Refer to Flushing .

Was the repair complete?

Go to Step 22

--

Check the engine oil.

Is the engine oil foamy and/or milky?

Go to Step 20

--

1. Remove the cylinder head. Refer to Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side in Engine Mechanical - 4.3L, Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side in Engine Mechanical - 4.8L, 5.3L and 6.0L, Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side in Engine Mechanical - 6.6L, or Cylinder Head Replacement - Left Side or Cylinder Head Replacement - Right Side in Engine Mechanical - 8.1L.
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 in Engine Mechanical - 8.1 L.
3. Inspect the cylinder head and block for cracks.

Was a damaged/faulty component found?

Go to Step 21

--

Replace and/or repair the component as necessary.

Was the repair complete?

Go to Step 22

--

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

Does the engine overheat?

--

System OK