Reference Information
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
- «Circuit Testing»(ref-301517-S12739748792008101700000)
- «Connector Repairs»(ref-301517-S02286547552008101700000)
- «Wiring Repairs»(ref-301517-S19995224182008101700000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- «Cooling Fan and Shroud Replacement»(ref-301507-S40014758652008101700000)
- «Control Module References»(ref-301518-S12838675482008101700000) for ECM replacement, setup, and programming
Description and Operation
- «Cooling Fan Description and Operation»(ref-301507-S27746712852008101700000)
- «Instrument Cluster Description and Operation»(ref-301489-S37827132822008101700000)
- «Indicator/Warning Message Description and Operation»(ref-301489-S39521947202008101700000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
- If DTC P0480 or P0481 are set, diagnose those DTCs first.
- Observe the engine coolant level. The engine coolant level should be within the operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual.
- Ensure that the vehicle has the correct engine coolant with correct concentration and is not old, contaminated, or contains additives. Refer to Recommended Fluids and Lubricants in the Owner's Manual.
- Inspect the cooling system for the following: Leaks Kinked or pinched hoses, especially at the radiator Loose, missing, or damaged radiator air seals or deflectors Air flow obstructions or bent fins at the radiator or the A/C condenser-Refer to «Symptoms - Engine Cooling»(ref-301507-S20032770212008101700000) .
- Command the cooling fans ON and OFF, low and high speed. The engine cooling fans should turn ON and OFF with each command. If the cooling fans do not function as indicated, refer to «Cooling Fan Inoperative»(ref-301507-S36875022582008101700000) .
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Identifying Intermittent Conditions
Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition
- Moisture and water intrusion in connectors, terminals, and components
- Connector mating
- Terminal contact
- High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
- Harness that is located too tight, or chaffed circuits
- High or low ambient temperature
- High or low engine coolant temperatures
- High underhood temperatures
- Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load
- High or low system voltage
- High vehicle load conditions
- Rough road surface
- Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
- Incorrect installation of non-factory, aftermarket, and after factory add on accessories
If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
- «Circuit Testing»(ref-301517-S12739748792008101700000)
- «Connector Repairs»(ref-301517-S02286547552008101700000)
- «Wiring Repairs»(ref-301517-S19995224182008101700000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
- Verify that the following DTCs are not set: P0480, P0481. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-301515-S23532461582008101700000) .
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fans are not activated.
- «Cooling Fan and Shroud Replacement»(ref-301507-S40014758652008101700000)
- «Control Module References»(ref-301518-S12838675482008101700000) for ECM replacement, setup, and programming
Repair Verification
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
- «Circuit Testing»(ref-301517-S12739748792008101700000)
- «Connector Repairs»(ref-301517-S02286547552008101700000)
- «Wiring Repairs»(ref-301517-S19995224182008101700000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
- If DTCs P0480 or P0481 are set, then perform those diagnostics first.
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.
- «Cooling Fan and Shroud Replacement»(ref-301507-S40014758652008101700000)
- «Control Module References»(ref-301518-S12838675482008101700000) for ECM replacement, setup, and programming
Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fans turn ON and OFF with each command.
Engine Overheating
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: Either of the following conditions indicate a probable engine overheat condition. The engine temperature gage is in the red (overheat) zone and/or the engine temperature indicator is ON. Hot engine coolant overflows from the coolant recovery reservoir and/or radiator cap onto the ground while the engine is running. | |||
| 1 | Inspect and fill the cooling system, as necessary. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . Inspect the cooling system for leaks, as necessary. Repair the cooling system leaks, as necessary. Has the inspection/repair been performed? | Go to Step 2 | |
| 2 | Start the engine and allow the engine to run at approximately 1,200 RPM. Use the Scan Tool in order to verify the overheat condition. Does the Scan Tool verify the engine overheat condition? | Go to Step 3 | Go to Diagnostic System Check - Vehicle |
| 3 | Verify that the cooling fans are operating properly. Repair the cooling fan system, as necessary. Does the engine still overheat? | Go to Step 4 | System OK |
| 4 | Perform the following inspections: Inspect the radiator and the A/C condenser cooling fins for debris or any other obstruction. Inspect the drive belt system and the drive belt tensioner for proper operation in order to ensure that the coolant pump is rotating properly. Inspect for loose, damaged and/or missing air deflector(s). Check for a pinched or kinked cooling system hose. Repair the systems as necessary. Does the engine still overheat? | Go to Step 5 | System OK |
| 5 | Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Is the thermostat operating properly? | Go to Step 7 | Go to Step 6 |
| 6 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (LY7) or Engine Coolant Thermostat Replacement (LAT) or Engine Coolant Thermostat Replacement (LZ4) . Does the engine still overheat? | Go to Step 7 | System OK |
| 7 | IMPORTANT: Excessive coolant freeze point protection MAY cause the coolant to boil at low temperatures. Inspect for the proper coolant concentration (mixture). Correct the coolant concentration as necessary. Remove the radiator cap. Start the engine and inspect for a constant flow of air bubbles in the engine coolant. Is there a constant flow of air bubbles in the engine coolant? | Go to Step 8 | Go to Step 9 |
| 8 | The probable cause of the engine overheat is combustion chamber gasses leaking into the cooling system. This condition is usually caused by the following: A worn or damaged cylinder head gasket A worn or damaged cylinder head A worn and/or damaged engine block Verify this condition by inspecting the spark plug electrodes and porcelain surrounding the spark plug electrode for signs of coolant. Replace and/or repair the engine internal component(s), as necessary, in order to repair the engine internal coolant leak. Does the engine still overheat? | Go to Step 1 | System OK |
| 9 | The engine overheat may be caused by a cooling system blockage. Flush the cooling system. Refer to Coolant System Flushing . Does the engine still overheat? | Go to Step 10 | System OK |
| 10 | IMPORTANT: It is unlikely that the water pump is the cause of the overheat condition. If NONE of the cooling system passages are restricted, replace the coolant pump. Refer to Water Pump Replacement (LY7) or Water Pump Replacement (LAT) or Water Pump Replacement (LZ4) .Does the engine still overheat? | Go to Step 1 | System OK |
| IMPORTANT |
|---|
| Excessive coolant freeze point protection MAY cause the coolant to boil at low temperatures. |
| IMPORTANT |
|---|
| It is unlikely that the water pump is the cause of the overheat condition. |
Loss of Coolant
| 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 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 (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . 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 28 |
| 6 | Engine overheating can cause a loss of coolant. Is the engine overheating? | Go to Step 29 | 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 31 | Go to Step 8 |
| 8 | Idle the engine at normal operating temperature. 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 30 | Go to Step 10 |
| 10 | CAUTION: Refer to Moving Parts and Hot Surfaces Caution . With the engine idling, inspect the surge tank.Does the surge tank 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 surge tank Heater core Radiator Are any of the hoses, clamps or pipes leaking? | Go to Step 22 | Go to Step 12 |
| 12 | Visually inspect the following components: The coolant pressure cap The core plugs The cylinder head gaskets The engine block The intake manifold The radiator The thermostat housing The water pump Are any of the listed components leaking? | Go to Step 22 | Go to Step 13 |
| 13 | Pressure test the cooling system. Refer to Cooling System Leak Testing . With the cooling system pressurized, visually inspect the components listed in steps 11 and 12. Are any leaks present? | Go to Step 22 | 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 23 |
| 15 | Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure? | Go to Step 32 | Go to Step 23 |
| 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 24 | Go to Step 17 |
| 17 | Add 30 ml (1 oz) of Extended Life Coolant Leak Detection Dye GM P/N 89022219 (Canadian P/N 89022220) to the cooling system for each 15 liters (4 gallons) of coolant. Refer to Approximate Fluid Capacities (BAS/Hybrid) or Approximate Fluid Capacities (AURA) . Start the vehicle and allow the engine to reach normal operating temperature. Shut the engine off. Use J 42220 Universal 12V Leak Detection Lamp to visually inspect the components listed in steps 11 and 12. See Special Tools . Are any leaks present? | Go to Step 22 | Go to Step 18 |
| 18 | Use J 42220 to inspect for the following conditions:. See Special Tools . Coolant dye in the HVAC module drain tube Coolant dye on the vehicle floor covering near the HVAC module Is coolant dye present? | Go to Step 24 | Go to Step 19 |
| 19 | Inspect the underside of the engine oil fill cap for a gray/white milky substance. Is there a milky substance on under the oil fill cap? | Go to Step 20 | Go to Step 21 |
| 20 | 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 30 | Go to Step 21 |
| 21 | 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 25 | Go to Step 33 |
| 22 | Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete? | Go to Step 33 | |
| 23 | Replace the coolant pressure cap. Is the repair complete? | Go to Step 33 | |
| 24 | Replace the heater core. Refer to Heater Core Replacement . Is the repair complete? | Go to Step 33 | |
| 25 | Remove the transmission oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the transmission oil cooler for coolant. Is coolant present? | Go to Step 26 | Go to Step 27 |
| 26 | Replace the radiator. Refer to Radiator Replacement (LY7) or Radiator Replacement (LZ4/LAT) or Radiator Replacement (LE5) . Service the automatic transmission. Refer to the appropriate procedure: Engine Coolant/Water in Transmission for the 4T45-E transaxle Engine Coolant/Water in Transmission for the 6T70/6T75 transmission Is the repair complete? | Go to Step 33 | |
| 27 | Install the cooler lines to the radiator. Is the action complete? | Go to Step 33 | |
| 28 | Repair the engine no crank condition. Refer to the appropriate procedure: Engine Will Not Crank - Crankshaft Will Not Rotate for the 2.4L engine Engine Will Not Crank - Crankshaft Will Not Rotate for the 3.5L engine Engine Will Not Crank - Crankshaft Will Not Rotate for the 3.6L engine Is the repair complete? | Go to Step 33 | |
| 29 | Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete? | Go to Step 33 | |
| 30 | Repair the engine internal coolant leak. Refer to the appropriate procedure: Coolant in Combustion Chamber or Coolant in Engine Oil for the 2.4L engine Coolant in Combustion Chamber or Coolant in Engine Oil for the 3.5L engine Coolant in Combustion Chamber or Coolant in Engine Oil for the 3.6L engine Is the repair complete? | Go to Step 33 | |
| 31 | Repair the engine knock. Refer to the appropriate procedure: Lower Engine Noise, Regardless of Engine Speed for the 2.4L engine Lower Engine Noise, Regardless of Engine Speed for the 3.5L engine Lower Engine Noise, Regardless of Engine Speed for the 3.6L engine Is the repair complete? | Go to Step 33 | |
| 32 | Repair the combustion pressure in the cooling system problem. Refer to the appropriate procedure: Coolant in Combustion Chamber for the 2.4L engine Coolant in Combustion Chamber for the 3.5L engine Coolant in Combustion Chamber for the 3.6L engine Is the repair complete? | Go to Step 33 | |
| 33 | Operate the system in order to verify the repair. Did you find and correct the condition? | System OK | Go to Step 2 |
| CAUTION |
|---|
| Refer to Moving Parts and Hot Surfaces Caution . |
Electrical Information Reference
- «Circuit Testing»(ref-301517-S12739748792008101700000)
- «Connector Repairs»(ref-301517-S02286547552008101700000)
- «Wiring Repairs»(ref-301517-S19995224182008101700000)
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- «Coolant Heater Replacement (LY7)»(ref-301507-S00405536512008101700000) or «Coolant Heater Replacement (LZ4)»(ref-301507-S29574474542008101700000) or «Coolant Heater Replacement (LAT)»(ref-301507-S40966425422008101700000)
- «Coolant Heater Cord Replacement (LAT)»(ref-301507-S26644749722008101700000) or «Coolant Heater Cord Replacement (LZ4)»(ref-301507-S17196006742008101700000) or «Coolant Heater Cord Replacement (LY7)»(ref-301507-S12662273162008101700000)
Engine Fails To Reach Normal Operating Temperature
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Ensure that the cooling system is full. Allow the engine to cool. Start the engine. Turn the air conditioning system off. Inspect the engine cooling fan(s). Is the electric cooling fan on? | Go to Step 2 | Go to Step 3 |
| 2 | Diagnose and repair the cooling fan system. Refer to Cooling Fan Always On . Verify the customer complaint. Does the engine still fail to reach normal operating temperature? | Go to Step 3 | System OK |
| 3 | Install the Scan Tool to the DLC. Compare the Scan Tool coolant temperature reading to the I/P cluster coolant temperature. Is the I/P cluster coolant temperature close to the reading on the Scan Tool? | Go to Step 5 | Go to Step 4 |
| 4 | Diagnose and repair the coolant temperature gage system. Verify the customer complaint. Does the engine still fail to reach normal operating temperature? | Go to Step 5 | System OK |
| 5 | Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Is the thermostat operating properly? | Go to Step 1 | Go to Step 6 |
| 6 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (LY7) or Engine Coolant Thermostat Replacement (LAT) or Engine Coolant Thermostat Replacement (LZ4) . Verify the customer complaint. Does the engine still fail to reach normal operating temperature? | Go to Step 1 | System OK |
Filling Procedure
- Slowly add a mixture of 50/50 DEX-COOL antifreeze and clean water to the coolant surge tank. Fill the cooling system as indicated below: For LE5/LAT vehicles when the engine block is not drained, add 3.5 liters (3.7 qts) For LE5/LAT vehicles when the engine block is drained, add 6 liters (6.3 qts) For LZ4/LY7 vehicles, add 5 liters (5.3 qts)
- Start the engine and check for leaks.
- Run the engine and cycle the vehicle from idle to 3,000 RPM in 30 second intervals until the engine cooling fan comes ON, the engine cooling fan turns ON at approximately 102°C (216°F). Repeat this process twice before the engine is turned OFF.
- Return the engine to idle, and idle for 30 seconds, then turn the engine OFF.
- Allow the vehicle to cool, before adding additional coolant.
- Add additional coolant to the surge tank until the level is approximately 13 mm (0.5 in) above the surge tank seam.
- Install the coolant surge tank cap.
Radiator Cleaning
| CAUTION | NEVER spray water on a hot radiator. The resulting steam could cause personal injury. |
Note. The radiator fins are necessary for good heat transfer. Do not brush the fins. This may cause damage to the fins, reducing heat transfer.
- Some conditions may require the use of warm water and a mild detergent.
- Clean the A/C condenser fins.
- Clean between the A/C condenser and radiator.
- Clean the radiator cooling fins.
- Straighten any damaged cooling fins.
Scheme 27
| Callout | Component Name |
|---|---|
| CAUTION: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. Preliminary Procedures: Partially drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . | |
| 1 | Radiator Surge Tank Assembly Nut (Qty: 2) NOTE: Refer to Fastener Notice . Tighten: 6 N.m (53 lb in) |
| 2 | Radiator Surge Tank Hose Clamp (Qty: 2) Special Tools: J 38185 Hose Clamp Pliers. See Special Tools . |
| 3 | Radiator Surge Tank Assembly |
| CAUTION |
|---|
| With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. |
| NOTE |
|---|
| Refer to Fastener Notice . |
Scheme 28
| Callout | Component Name |
|---|---|
| CAUTION: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. Preliminary Procedures Partially drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . Remove the intake manifold cover. Refer to Intake Manifold Cover Replacement . | |
| 1 | Surge Tank Inlet Hose Procedure: Reposition the 2 surge tank hose clamps using the J 38185 . See Special Tools . Special Tools: J 38185 Hose Clamp Pliers. See Special Tools . |
| CAUTION |
|---|
| With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. |
Scheme 29
| Callout | Component Name |
|---|---|
| CAUTION: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. Preliminary Procedures: Partially drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . | |
| 1 | Surge Tank Inlet Hose Clamp (Qty: 2) Special Tools: J 38185 Hose Clamp Pliers. See Special Tools . |
| 2 | Surge Tank Inlet Hose |
| CAUTION |
|---|
| With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. |
Scheme 30
| Callout | Component Name |
|---|---|
| CAUTION: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. Preliminary Procedures Partially drain the cooling system. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (GE 47716 Fill) . Reposition the surge tank hose clamp (Qty: 2) using J 38185 . See Special Tools . | |
| 1 | Radiator Surge Tank Inlet Hose |
| CAUTION |
|---|
| With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result. |
Tools Required
J 38185 Hose Clamp Pliers. See Special Tools .
EN 46104 Water Pump Pulley Holding Tool
J 43651 Water Pump Holding Tool. See Special Tools .
J 38185 Hose Clamp Pliers. See Special Tools .
J 38185 Hose Clamp Pliers. See Special Tools .
Cooling Fan Control
The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) or engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G106.
During low speed operation, the PCM or ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM or ECM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM or ECM supplies a ground path for the cooling fan 2 relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan S/P relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
The PCM or ECM commands Low Speed Fans ON under the following conditions
- Engine coolant temperature exceeds approximately 106°C (223°F).
- When A/C is requested and the ambient temperature is more than 50°C (122°F).
- A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
- After the vehicle is shut off, if the engine coolant temperature at key-off is more than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.
The PCM or ECM commands High Speed Fans ON under the following conditions
- Engine coolant temperature reaches 110°C (230°F).
- A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
- When certain DTCs set
Engine Coolant Indicators
TEMP
- The instrument panel cluster (IPC) illuminates the TEMP indicator when the powertrain control module (PCM) or engine control module (ECM) determines that the coolant temperature is more than 128°C (262°F). The IPC receives a discrete input from the PCM or ECM requesting illumination.
- The IPC performs the display test at the start of each ignition cycle. The IPC illuminates the TEMP indicator.
Coolant Level Control
The engine cooling system contains an engine coolant level switch to alert the driver in the event of a low coolant level. When the engine coolant level in the surge tank falls below a certain level, the coolant level switch opens. When the body control module (BCM) detects an open or a high voltage level on the coolant level indicator control circuit, for at least 10 seconds, it will send a GM LAN message to the driver information center (DIC) requesting display of the low coolant level message. There is approximately a 10-second delay before the BCM sends the GM LAN message to prevent the message from being displayed, due to coolant sloshing in the surge tank.
Coolant Heater
The optional engine coolant heater (RPO K05) operates using AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather -29°C (-20°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the coolant does not flow to the radiator until the thermostat opens. This allows the engine to warm quickly.
Cooling Cycle
Coolant flows from the radiator outlet and into the water pump inlet. Some coolant flows from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost capability as the coolant warms up.
Coolant also flows from the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where the coolant absorbs heat.
The coolant then flows through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where the coolant absorbs additional heat.
Coolant is also directed to the throttle body. There the coolant circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body.
From the cylinder heads, the coolant flows to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine reaches normal operating temperature, or the coolant will flow through the thermostat and into the radiator where the coolant is cooled. At this point, the coolant flow cycle is completed.
Efficient operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components.
Coolant
The engine coolant is a solution made up of a 50/50 mixture of DEX-COOL and suitable drinking water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.
Radiator
The radiator is a heat exchanger consisting of a core and 2 tanks. The aluminum core is a tube and fin crossflow design that extends from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer to the atmosphere.
The inlet and outlet tanks are a molded, high temperature, nylon reinforced plastic material. A high temperature rubber gasket seals the tank flange edge to the aluminum core. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core.
The radiator also has a drain cock located in the bottom of the left hand tank. The drain cock unit includes the drain cock and drain cock seal.
Heat is removed from the coolant as the coolant passes through the radiator. The fins on the core transfer heat from the coolant passing through the tubes. Air passing between the fins absorbs the heat and cools the coolant.
Pressure Cap
The pressure cap seals and pressurizes the cooling system. The cap contains a blow off, or pressure valve and a vacuum, or an atmospheric valve
- The pressure valve is held against the seat by a spring that protects the radiator by relieving pressure that exceeds 15 psi.
- The vacuum valve is held against the seat by a spring that permits opening of the valve to relieve vacuum created when the cooling system cools. The vacuum, if not relieved, might cause the radiator to collapse.
The pressure cap allows the cooling system pressure to build up when the temperature increases. As the pressure builds, the boiling point of the coolant increases. Therefore, the engine coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant becomes, the faster the heat transfers from the radiator into the cooler air.
The pressure in the cooling system can get too high. When the pressure exceeds the strength of the spring, the pressure valve rises, venting the excess pressure.
As the engine cools, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open. This equalizes the pressure in the cooling system with the atmospheric pressure, preventing the radiator from collapsing.
Coolant Recovery System
The coolant recovery system consists of a plastic coolant recovery reservoir and overflow tube. The recovery reservoir is also called a recovery tank or expansion tank. This tank is partially filled with coolant and is connected to the radiator fill neck with the overflow tube. Coolant can flow back and forth between the radiator and the reservoir.
In effect, a cooling system with a coolant recovery reservoir is a closed system. When the pressure within the cooling system gets too high, the pressure valve in the pressure cap will open. This allows the coolant, which has expanded due to heat, to flow through the overflow tube and into the recovery reservoir. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum opens the vacuum valve in the pressure cap, allowing some of the coolant in the reservoir to be siphoned back into the radiator. Under normal operating conditions, no coolant is lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. An advantage to using a coolant recovery reservoir is the elimination of almost all air bubbles from the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Air Baffles and Seals
The cooling system uses deflectors, air baffles and air seals to increase cooling system capability. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle and through the radiator to increase engine cooling. Air baffles are also used to direct airflow through the radiator and increase cooling capability. Air seals prevent air from bypassing the radiator and A/C condenser, and prevent recirculation of hot air for better hot weather cooling and A/C condenser performance.
Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is a flat plate mounted on the pump shaft with a series of flat or curved blades or vanes. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings, which never need to be lubricated. With a sealed bearing, grease cannot leak out, and dirt and water cannot get in.
The water pump circulates coolant throughout the cooling system. The pump is driven by the crankshaft from the drive belt.
Thermostat
The thermostat is a coolant flow control component, whose purpose is to regulate the operating temperature of the engine. The thermostat utilizes a temperature sensitive wax-pellet element, which connects to a valve through a piston. Heating causing the element to expand and exert pressure against a rubber diaphragm. This pressure forces the valve to open. Cooling causes the element to contract. This contraction allows a spring to push the valve closed.
When the coolant temperature is below 91°C (195°F), the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, even after opening. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger and is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the transmission fluid passes through the cooler.
The transmission oil pump circulates the fluid through the feed line to the oil cooler. The fluid then flows through the cooler while the engine coolant absorbs heat from the fluid. The fluid is then pumped through the return line to the transmission.