GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 Lucerne 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic 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 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

--

5

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

Does the engine crankshaft rotate?

Go to Step 6

Go to Step 26

6

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 27

Go to Step 7

7

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

Is the engine knocking?

Go to Step 29

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 28

Go to Step 10

10

With the engine idling, inspect the surge tank system.

Does the surge tank 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:

    • Coolant crossover
    • Engine
    • Surge tank
    • Heater core
    • Radiator

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

Go to Step 20

Go to Step 12

12

Visually inspect the following components:

    • Coolant pressure cap
    • Core plugs
    • Cylinder head gaskets
    • Engine block
    • Intake manifold
    • Radiator
    • Thermostat housing
    • Water pump

Are any of the listed components leaking?

Go to Step 20

Go to Step 13

13
  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 11 and 12.

Are any leaks present?

Go to Step 20

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 21

15

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

Does the coolant pressure cap hold pressure?

Go to Step 30

Go to Step 21

16

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 22

Go to Step 17

17

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 18

Go to Step 19

18

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 28

Go to Step 19

19

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 23

Go to Step 31

20

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

Is the repair complete?

Go to Step 31

--

21

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 31

--

22

Replace the heater core. Refer to Heater Core Replacement.

Is the repair complete?

Go to Step 31

--

23
  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?

Go to Step 24

Go to Step 25

24
  1. Replace the radiator. Refer to Radiator Replacement.
  2. Service the automatic transmission. Refer to Engine Coolant/Water in Transmission for the 4T80-E transaxle or Engine Coolant/Water in Transmission for the 4T65-E transaxle.

Is the repair complete?

Go to Step 31

--

25

Install the cooler lines to the radiator.

Is the action complete?

Go to Step 31

--

26

Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate for the 4.6L engine or Engine Will Not Crank - Crankshaft Will Not Rotate for the 3.8L engine.

Is the repair complete?

Go to Step 31

--

27

Repair the engine overheating condition. Refer to Engine Overheating.

Is the repair complete?

Go to Step 31

--

28

Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber or Coolant in Engine Oil for the 4.6L engine or Coolant in Combustion Chamber or Coolant in Engine Oil for the 3.9L engine.

Is the repair complete?

Go to Step 31

--

29

Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed for the 4.6L engine or Lower Engine Noise, Regardless of Engine Speed for the 3.9L engine.

Is the repair complete?

Go to Step 31

--

30

Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test for the 4.6L engine or Cylinder Leakage Test for the 3.9L engine.

Is the repair complete?

Go to Step 31

--

31

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2