DEFINITION: The cooling system is losing 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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Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 19

Go to Step 6

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 7

Go to Step 8

Does the white smoke have a burning coolant type odor?

Go to Step 20

Go to Step 8

Visually inspect the hoses, pipes and hose clamps.

Are any of the hoses, clamps or pipes leaking?

Go to Step 21

Go to Step 9

Visually inspect the following components:

Are any of the listed components leaking?

Go to Step 21

Go to Step 10

1. Pressure test the cooling system. Refer to Cooling System Leak Testing .
2. With the cooling system pressurized, visually inspect the components listed in steps 7 and 8.

Are any leaks present?

Go to Step 21

Go to Step 11

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

Does the coolant pressure cap hold pressure?

Go to Step 12

Go to Step 16

Inspect for the following conditions:

Is coolant present?

Go to Step 21

Go to Step 13

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

Is there a milky substance under the oil fill cap?

Go to Step 14

Go to Step 15

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 17

Go to Step 15

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 18

Go to Step 22

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 22

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

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

•	Engine Oil and Oil Filter Replacement for the 4.8L, 5.3L, and 6.0L engine

•	Engine Oil and Oil Filter Replacement for the 6.6L (LLY) engine

•	Engine Oil and Oil Filter Replacement for the 8.1L engine

Is the repair complete?

Go to Step 22

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1. Replace the radiator. Refer to Radiator Replacement .
2. Service the automatic transmission. Refer to one of the following procedures:

•	Engine Coolant/Water in Transmission for the 4L60-E/4L65-E transmission

•	Engine Coolant/Water in Transmission for the 4L80-E/4L85-E transmission

Is the repair complete?

Go to Step 22

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Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 22

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Repair the engine internal coolant leak. Refer to one of the following procedures:

Is the repair complete?

Go to Step 22

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

Is the repair complete?

Go to Step 22

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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