DEFINITION: The cooling system is loosing coolant either internally or externally.

Were you sent here from Symptoms or another diagnostic table?

Go to Step 2

Go to Symptoms - Engine Cooling

Repair any present DTCs. Refer to Diagnostic System Check - Vehicle .

Is the action complete?

Go to Step 3

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Inspect the coolant level.

Is the coolant at the proper level?

Go to Step 5

Go to Step 4

Fill the cooling system to the proper level. Refer to Cooling System Draining and Filling .

Is the action complete?

Go to Step 5

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If the engine is suspected to have a coolant leak into the cylinder, the coolant can hydraulically lock the cylinder.

Does the engine crankshaft rotate?

Go to Step 6

Go to Step 32

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 33

Go to Step 7

Extended engine operation with a low coolant level can cause engine internal component failure.

Is the engine knocking?

Go to Step 35

Go to Step 8

1. Idle the engine at normal operating temperature.
2. Inspect for heavy white smoke coming out of the exhaust pipe.

Is a heavy white smoke present from the exhaust pipe?

Go to Step 9

Go to Step 10

Does the white smoke have a burning coolant type odor?

Go to Step 34

Go to Step 10

With the engine idling, inspect the coolant recovery system.

Does the coolant recovery system discharge coolant while the engine is idling?

Go to Step 15

Go to Step 11

Visually inspect the hoses, pipes and hose clamps at the following locations:

Are any of the hoses, clamps, or pipes leaking?

Go to Step 23

Go to Step 12

Visually inspect the following components:

Are any of the listed components leaking?

Go to Step 23

Go to Step 13

1. Pressure test the cooling system. Refer to Cooling System Leak Testing .
2. Visually inspect the components listed in steps 11 and 12 again.

Are any leaks present?

Go to Step 23

Go to Step 14

Pressure test the coolant pressure cap. Refer to Pressure Cap Testing .

Does the coolant pressure cap hold pressure?

Go to Step 16

Go to Step 24

Pressure test the coolant pressure cap. Refer to Pressure Cap Testing .

Does the coolant pressure cap hold pressure?

Go to Step 36

Go to Step 24

Inspect for the following conditions:

Is coolant present?

Go to Step 25

Go to Step 17

If equipped with auxiliary heating, inspect for the following:

Is coolant present?

Go to Step 26

Go to Step 20

1. Add 30 ml (1 oz) of Part Number 89022219 USA/89022220 Canada Extended Life Coolant Leak Detection Dye to the cooling system for each 15 liters (4 gallons) of coolant. Refer to Approximate Fluid Capacities .
2. Start the vehicle and allow the engine to reach normal operating temperature.
3. Shut the engine Off.
4. Use J 42220 to visually inspect the components listed in steps 11 and 12.

Are any leaks present?

Go to Step 23

Go to Step 19

Use J 42220 to inspect for the following conditions:

Is coolant dye present?

Go to Step 25

Go to Step 20

Inspect the underside of the oil fill cap for a gray/white milky substance.

Is there a milky substance under the oil fill cap?

Go to Step 21

Go to Step 22

Inspect the engine oil fluid level indicator for a gray/white milky substance.

Is there a milky substance on the engine oil fluid level indicator?

Go to Step 27

Go to Step 22

Inspect the automatic transmission oil fluid level indicator, if equipped, for a gray/white milky substance.

Is there a milky substance on the automatic transmission fluid level indicator?

Go to Step 29

Go to Step 37

Repair or replace the leaking component. Refer to the appropriate repair.

Is the repair complete?

Go to Step 37

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Replace the coolant pressure cap.

Is the repair complete?

Go to Step 37

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Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 37

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Replace the auxiliary heater core. Refer to Auxiliary Heater Core Replacement .

Is the repair complete?

Go to Step 37

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1. Remove the engine oil cooler lines from the radiator.
2. Pressure test the cooling system. Refer to Cooling System Leak Testing .
3. Inspect the engine oil cooler for coolant.

Is coolant present in the engine oil cooler?

Go to Step 28

Go to Step 31

1. Replace the radiator. Refer to Radiator Replacement
2. Service the engine oil and filter. Refer to the following:

•	Engine Oil and Oil Filter Replacement for the 4.3L engine.

•	Engine Oil and Oil Filter Replacement for the 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L engines.

•	Engine Oil and Oil Filter Replacement for the 6.6L engine.

Is the repair complete?

Go to Step 37

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1. Remove the transmission oil cooler lines from the radiator.
2. Pressure test the cooling system. Refer to Cooling System Leak Testing .
3. Inspect the transmission oil cooler for coolant.

Is coolant present in the transmission oil cooler?

Go to Step 30

Go to Step 31

1. Replace the radiator. Refer to Radiator Replacement .
2. Service the automatic transmission. Refer to Engine Coolant/Water in Transmission for the 4L60-E transmission, or Engine Coolant/Water in Transmission for the 4L80-E transmission.

Is the repair complete?

Go to Step 37

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Install the cooler lines to the radiator.

Is the action complete?

Go to Step 37

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Repair the engine no crank condition. Refer to the following: .

Is the repair complete?

Go to Step 37

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Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 37

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Repair the engine internal coolant leak. Refer to the following:

Is the repair complete?

Go to Step 37

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Repair the engine knock. Refer to the following:

Is the repair complete?

Go to Step 37

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Repair the combustion pressure in the cooling system problem. Refer to the following:

Is the repair complete?

Go to Step 37

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Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2