GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Express 🢒 Engine 🢒 Engine Cooling 🢒 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

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3

Inspect the coolant level.

Is the coolant at the proper level?

Go to Step 6

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

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5

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 30

6

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 31

Go to Step 7

7

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

Is the engine knocking?

Go to Step 33

Go to Step 8

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

9
    • 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 32

Go to Step 10

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

11

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

    • Auxiliary heater
    • Coolant bypass
    • Coolant crossover
    • Coolant reservoir
    • Heater
    • Hot water shut-off valve
    • Radiator

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

Go to Step 21

Go to Step 12

12

Visually inspect the following components:

    • Coolant pressure cap
    • Coolant reservoir
    • Core plugs
    • Cylinder head gaskets
    • Engine block
    • Hot water shut-off valve
    • Intake manifold
    • Radiator
    • Thermostat
    • Water pump

Are any of the listed components leaking?

Go to Step 21

Go to Step 13

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 21

Go to Step 14

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 22

15

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

Does the coolant pressure cap hold pressure?

Go to Step 34

Go to Step 22

16

Inspect for the following conditions:

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

Is coolant present?

Go to Step 23

Go to Step 17

17

If equipped with auxiliary heating, inspect for the following:

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

Is coolant present?

Go to Step 24

Go to Step 18

18

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 19

Go to Step 20

19

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 25

Go to Step 20

20

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 27

Go to Step 35

21

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

Is the repair complete?

Go to Step 35

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22

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 35

--

23

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 35

--

24

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

Is the repair complete?

Go to Step 35

--

25
  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 26

Go to Step 29

26
  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 35

--

27
  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 28

Go to Step 29

28
  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 35

--

29

Install the cooler lines to the radiator.

Is the action complete?

Go to Step 35

--

30

Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate .

Is the repair complete?

Go to Step 35

--

31

Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 35

--

32

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

Is the repair complete?

Go to Step 35

--

33

Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed .

Is the repair complete?

Go to Step 35

--

34

Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test .

Is the repair complete?

Go to Step 35

--

35

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2