GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2008 🢒 H2 🢒 General Information 🢒 General Information 🢒 Loss of Coolant

Step

Action

Yes

No

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

1

Were you sent here from Symptoms, or another diagnostic table?

Go to Step 2

Go to Symptoms - Engine Cooling

2

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

Is the action complete?

Go to Step 3

--

3

Inspect the coolant level.

Is the coolant at the proper level?

Go to Step 5

Go to Step 4

4

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

Is the action complete?

Go to Step 5

--

5

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 19

Go to Step 6

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

7
    • Coolant in the exhaust system creates a distinctive, burning coolant odor in the exhaust.
    • Condensation in the exhaust system can cause an odorless white smoke during engine warm up.

Does the white smoke have a burning coolant type odor?

Go to Step 20

Go to Step 8

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

9

Visually inspect the following components:

    • Block heater
    • Coolant pressure cap
    • Core plugs
    • Throttle Body
    • Engine block
    • Intake manifold
    • Radiator
    • Thermostat housing
    • Water pump

Are any of the listed components leaking?

Go to Step 21

Go to Step 10

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

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

12

Inspect for the following conditions:

    • A coolant smell inside of the vehicle
    • Coolant in the HVAC module drain tube
    • Coolant on the vehicle floor covering near the HVAC module

Is coolant present?

Go to Step 21

Go to Step 13

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

14

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

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

16

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 22

--

17
  1. Replace the radiator. Refer to Radiator Replacement .
  2. Service the engine oil and filter. Refer to Engine Oil and Oil Filter Replacement .

Is the repair complete?

Go to Step 22

--

18
  1. Replace the radiator. Refer to Radiator Replacement .
  2. Service the automatic transmission. Refer to Engine Coolant/Water in Transmission .

Is the repair complete?

Go to Step 22

--

19

Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 22

--

20

Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber and Coolant in Engine Oil .

Is the repair complete?

Go to Step 22

--

21

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

Is the repair complete?

Go to Step 22

--

22

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2