GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 STS 🢒 Body 🢒 Wiring Systems 🢒 Loss of Coolant

Loss of Coolant LH2 and LY7

Step

Action

Yes

No

DEFINITION: The cooling system is losing 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 Starting Point - Engine Cooling .

Is the action complete?

Go to Step 3

--

3

Inspect the coolant level at the surge tank.

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

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 22

6

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 23

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 25

Go to Step 8

8

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

    • Surge tank
    • Throttle body
    • Water pump
    • Heater core
    • Radiator

Are any of the hoses, clamps or pipes leaking?

Go to Step 18

Go to Step 9

9

Visually inspect the following components:

    • Block heater
    • Coolant pressure cap
    • Core plugs
    • Cylinder head gaskets
    • Cylinder heads
    • Engine block
    • Radiator
    • Thermostat housing
    • Water pump

Are any of the listed components leaking?

Go to Step 18

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 8 and 9.

Are any leaks present?

Go to Step 18

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 19

12
  1. Apply the parking brake.
  2. Ensure the vehicle is in PARK.
  3. Start and idle the engine until it reaches normal operating temperature.
  4. Inspect for heavy white smoke coming out of the exhaust pipe.

Is a heavy white smoke present from the exhaust pipe?

Go to Step 13

Go to Step 14

13
    • 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 24

Go to Step 14

14

With the engine idling, inspect the surge tank.

Does the surge tank discharge coolant while the engine is idling?

Go to Step 26

Go to Step 15

15

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 20

Go to Step 16

16

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

Is there a milky substance in the engine oil ?

Go to Step 24

Go to Step 17

17

Inspect the transmission oil fluid for a gray/white milky substance.

Does the transmission fluid contain a gray/white milky substance?

Go to Step 21

Go to Step 27

18

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

Is the repair complete?

Go to Step 27

--

19

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 27

--

20

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 27

--

21
  1. Replace the radiator. Refer to Radiator Replacement .
  2. Service the transmission. Refer to Engine Coolant/Water in Transmission .

Is the repair complete?

Go to Step 27

--

22

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

Is the repair complete?

Go to Step 27

--

23

Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 27

--

24

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

Is the repair complete?

Go to Step 27

--

25

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

Is the repair complete?

Go to Step 27

--

26

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

Is the repair complete?

Go to Step 27

--

27

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2

Loss of Coolant LC3

Step

Action

Yes

No

DEFINITION: The cooling system is losing 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 Starting Point - Engine Cooling .

Is the action complete?

Go to Step 3

--

3

Inspect the coolant level at the surge tank.

Is the coolant at the proper level?

Go to Step 4

Go to Step 5

4

Inspect the charge air cooling system coolant level.

Is the coolant at the proper level?

Go to Step 7

Go to Step 6

5

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

Is the action complete?

Go to Step 4

--

6

Fill the charge air cooling system to the proper level. Refer to Charge Air Cooling System Draining and Filling .

Is the action complete?

Go to Step 7

--

7

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 8

Go to Step 27

8

Engine overheating can cause a loss of coolant.

Is the engine overheating?

Go to Step 28

Go to Step 9

9

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

Is the engine knocking?

Go to Step 30

Go to Step 10

10

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

    • Radiator--Charge air cooler
    • Pump--Charge air cooler
    • Charge air cooler
    • Fill neck--Charge air cooler
    • Overflow reservoir--Charge air cooler

Are any of the hoses, clamps or pipes leaking?

Go to Step 23

Go to Step 11

11

Visually inspect the following components:

    • Radiator--Charge air cooler
    • Pump--Charge air cooler
    • Charge air cooler
    • Charge air coolant cap
    • Fill neck--Charge air cooler
    • Overflow reservoir--Charge air cooler

Are any of the listed components leaking?

Go to Step 23

Go to Step 12

12
  1. Pressure test the charge air cooling system. Refer to Cooling System Leak Testing .
  2. With the cooling system pressurized, visually inspect the components listed in steps 10 and 11.

Are any leaks present?

Go to Step 23

Go to Step 13

13

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

    • Surge tank
    • Throttle body
    • Water pump
    • Heater core
    • Radiator

Are any of the hoses, clamps or pipes leaking?

Go to Step 23

Go to Step 14

14

Visually inspect the following components:

    • Block heater
    • Coolant pressure cap
    • Core plugs
    • Cylinder head gaskets
    • Cylinder heads
    • Engine block
    • Radiator
    • Thermostat housing
    • Water pump

Are any of the listed components leaking?

Go to Step 23

Go to Step 15

15
  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 13 and 14.

Are any leaks present?

Go to Step 23

Go to Step 16

16

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

Does the coolant pressure cap hold pressure?

Go to Step 17

Go to Step 24

17
  1. Apply the parking brake.
  2. Ensure the vehicle is in PARK.
  3. Start and idle the engine until it reaches normal operating temperature.
  4. Inspect for heavy white smoke coming out of the exhaust pipe.

Is a heavy white smoke present from the exhaust pipe?

Go to Step 18

Go to Step 19

18
    • 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 29

Go to Step 19

19

With the engine idling, inspect the surge tank.

Does the surge tank discharge coolant while the engine is idling?

Go to Step 31

Go to Step 20

20

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 25

Go to Step 21

21

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

Is there a milky substance in the engine oil ?

Go to Step 29

Go to Step 22

22

Inspect the transmission oil fluid for a gray/white milky substance.

Does the transmission fluid contain a gray/white milky substance?

Go to Step 26

Go to Step 32

23

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

Is the repair complete?

Go to Step 32

--

24

Replace the coolant pressure cap.

Is the repair complete?

Go to Step 32

--

25

Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?

Go to Step 32

--

26
  1. Replace the radiator. Refer to Radiator Replacement .
  2. Service the transmission. Refer to Engine Coolant/Water in Transmission .

Is the repair complete?

Go to Step 32

--

27

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

Is the repair complete?

Go to Step 32

--

28

Repair the engine overheating condition. Refer to Engine Overheating .

Is the repair complete?

Go to Step 32

--

29

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

Is the repair complete?

Go to Step 32

--

30

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

Is the repair complete?

Go to Step 32

--

31

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

Is the repair complete?

Go to Step 32

--

32

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2