Engine Cooling System: Other GMC Cutaway G3500

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. If the ignition has been OFF for 8 h or greater, the IAT, the ambient air temperature, and the RCT should be within 9°C (16°F) of each other. Ignition ON, observe the scan tool IAT Sensor, Ambient Air Temperature, and the RCT sensor. Compare those sensor parameters to each other to determine if the condition is current.
2. Engine running, observe the RCT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current Ambient Air Temperature, the engine run time, and the vehicle operating conditions.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Module References»(ref-478463-S11680464072012061100000) for ECM replacement, setup, and programming
2. «Engine Coolant Temperature Sensor Replacement»(ref-478473-S26055245532012061100000)

Schematic Reference

Engine Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the DTC information with a scan tool. DTC P00B3, P00B4, P0117, or P0118 should not be set. If a DTC is set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-478441-S17310475232012061100000) for further diagnosis.
2. Verify the coolant in the radiator surge tank is at the correct level and there are no engine coolant leaks.
3. Engine idling for 15 min with the A/C OFF. NOTE: Depending on ambient temperature, it may take up to 4 min for the temperatures to equalize.
4. Increase the engine speed to 3 000 RPM. Observe the scan tool RCT and the ECT sensor parameters. The RCT and the ECT sensor parameters should be within 20°C (68°F).
5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Control Module References»(ref-478463-S11680464072012061100000) for ECM replacement, setup and programming
2. «Engine Coolant Temperature Sensor Replacement»(ref-478473-S26055245532012061100000)

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation (w/LGH)

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine operating, command the cooling fan clutch ON to 80 % and then OFF to 0 % with a scan tool. Observe the scan tool Test Status parameters listed below: FC Ckt Open Test Status FC Ckt Short Gnd Test Status FC Ckt Short Volts Test Status FC Ckt 2 Open Test Status FC Ckt 2 Short Gnd Test Status FC Ckt 2 Short Volts Test Status The parameters should display OK or Not Run in each of the commanded states.
2. Observe the DTC information with a scan tool. Verify DTC P0480 is not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-478473-S07171518262012061100000)
2. «Control Module References»(ref-478463-S11680464072012061100000) for ECM replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation (w/LGH)

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, inspect the cooling fan and the drive belt for the following conditions: A loose, worn, or mis-routed drive belt Oil leaks at the cooling fan clutch A free-spinning cooling fan A seized cooling fan clutch A broken cooling fan
2. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0480 or P0526 is not set. if a DTC is set diagnose that DTC first.
3. Operate the engine at 1,500 RPM while slowly commanding the cooling fan clutch from 10 % to 80 %, then return to 10 %. Observe the difference between the scan tool Fan Speed and Desired Fan Speed parameters throughout the test. The difference between the parameters should be less than 500 RPM throughout the speed transition.
4. Observe the DTC information with a scan tool. Verify DTC P0483 is not set.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-478473-S07171518262012061100000)
2. «Control Module References»(ref-478463-S11680464072012061100000) for replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation (w/LGH)

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, verify the fan clutch is not seized or binding.
2. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0480, P0483, or P0526 is not set, if a DTC is set diagnose that DTC first.
3. Engine idling at operating temperature with all accessories turned OFF, for greater than 10 minutes.
4. Observe the scan tool DTC information. Verify DTC P0495 is not set. If the DTC is set, replace the cooling fan clutch assembly.
5. Engine at operating temperature, Operate the engine at 1,500 RPM for 2 minutes. Observe the DTC information with a scan tool. Verify DTC P0495 is not set. If the DTC is set, replace the cooling fan clutch assembly.
6. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-478473-S07171518262012061100000)
2. «Control Module References»(ref-478463-S11680464072012061100000) for ECM replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation (w/LGH)

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P06D2 is not set. If the DTC is set, refer to «DTC P0641, P0651, P0697, P06A3, P06D2, or P06D6»(ref-478520-S23374711732012061100000) .
2. Engine operating, observe the scan tool Fan Speed parameter. The parameter should display a fan speed greater than 0 RPM.
3. Observe the DTC information with a scan tool. Verify DTC P0526 is not set.
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-478473-S07171518262012061100000)
2. «Control Module References»(ref-478463-S11680464072012061100000) for ECM replacement, setup, and programming

Description and Operation

1. «Cooling System Description and Operation»(ref-478473-S16406822202012061100000)
2. «Instrument Cluster Description and Operation»(ref-478458-S18856228382012061100000)
3. «Indicator/Warning Message Description and Operation»(ref-478458-S01316361242012061100000)
4. «Audible Warnings Description and Operation»(ref-478458-S03648411782012061100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to «Cooling System Draining and Filling (Static Fill)»(ref-478473-S36002101132012061100000) , «Cooling System Draining and Filling (Vac N Fill)»(ref-478473-S20462683752012061100000) , «Cooling System Draining and Filling (Static Fill Diesel)»(ref-478473-S09185496382012061100000) .
2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives. Refer to «Cooling System Draining and Filling (Static Fill)»(ref-478473-S36002101132012061100000) , «Cooling System Draining and Filling (Vac N Fill)»(ref-478473-S20462683752012061100000) , «Cooling System Draining and Filling (Static Fill Diesel)»(ref-478473-S09185496382012061100000) .
3. 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 The radiator and A/C condenser for any air flow obstructions or bent fins. Refer to «Engine Overheating»(ref-478473-S26348010992012061100000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the DTC information with a scan tool. DTC P00B3, P00B4, P00B6, P0117, P0118, P0480, or P0481 should not be set. If a DTC is set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-478441-S17310475232012061100000) for further diagnosis.
2. Verify the coolant in the radiator surge tank is at the correct level and there are no engine coolant leaks. Refer to «Cooling System Draining and Filling (Static Fill)»(ref-478473-S36002101132012061100000) , «Cooling System Draining and Filling (Vac N Fill)»(ref-478473-S20462683752012061100000) , «Cooling System Draining and Filling (Static Fill Diesel)»(ref-478473-S09185496382012061100000) , and «Loss of Coolant»(ref-478473-S25495354912012061100000) .
3. Increase the engine speed to 3000 RPM. Observe the scan tool ECT sensor parameter. The temperature should increase to greater than 102°C (215°F). If less than the specified value, replace the Engine Coolant Thermostat.
4. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Engine Coolant Thermostat Replacement (V6)

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

1. Moisture and water intrusion in connectors, terminals, and components
2. Connector mating
3. Terminal contact
4. High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
5. Harness that is located too tight, or chaffed circuits
6. High or low ambient temperature
7. High or low engine coolant temperatures
8. High underhood temperatures
9. Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load
10. High or low system voltage
11. High vehicle load conditions
12. Rough road surface
13. Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
14. 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 - INDEX

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-478470-S26306246352012061100000)
4. «Wiring Repairs»(ref-478470-S01823217952012061100000)

1. Ignition OFF, verify the radiator surge tank is filled to the correct level, with engine coolant.
2. Ignition ON, command the instrument cluster indicators ON and OFF with a scan tool. The low coolant indicator lamp should turn ON and OFF as commanded.
3. Engine operating, The low coolant indicator should be OFF with the engine coolant at the correct level.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Radiator Surge Tank Replacement»(ref-478473-S18271161932012061100000)
2. «Instrument Cluster Replacement»(ref-478458-S21478824792012061100000)
3. «Control Module References»(ref-478463-S11680464072012061100000)

Engine Overheating

Engine Overheating

Loss of Coolant

Loss of Coolant

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Wiring Repairs»(ref-478470-S01823217952012061100000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (V8 without 6.0L)»(ref-478473-S13751126962012061100000) , «Coolant Heater Replacement (V6)»(ref-478473-S02535834052012061100000) , «Coolant Heater Replacement (Diesel)»(ref-478473-S33947355422012061100000) , «Coolant Heater Replacement (V8)»(ref-478473-S37687437542012061100000)
2. «Coolant Heater Cord Replacement (V8)»(ref-478473-S08848534612012061100000) , «Coolant Heater Cord Replacement (Diesel)»(ref-478473-S35300319352012061100000) , «Coolant Heater Cord Replacement (V6)»(ref-478473-S36490589572012061100000)

Electrical Information Reference

1. «Circuit Testing»(ref-478470-S19131911002012061100000)
2. «Connector Repairs»(ref-478470-S01172177192012061100000)
3. «Wiring Repairs»(ref-478470-S01823217952012061100000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (V8 without 6.0L)»(ref-478473-S13751126962012061100000) , «Coolant Heater Replacement (V6)»(ref-478473-S02535834052012061100000) , «Coolant Heater Replacement (Diesel)»(ref-478473-S33947355422012061100000) , «Coolant Heater Replacement (V8)»(ref-478473-S37687437542012061100000)
2. «Coolant Heater Cord Replacement (V8)»(ref-478473-S08848534612012061100000) , «Coolant Heater Cord Replacement (Diesel)»(ref-478473-S35300319352012061100000) , «Coolant Heater Cord Replacement (V6)»(ref-478473-S36490589572012061100000)

Engine Fails To Reach Normal Operating Temperature

Engine Fails To Reach Normal Operating Temperature

Filling Procedure

1. Connect the lower radiator hose.
2. Using the «J 38185»(ref-478462-S20288722122012061100000) position the clamp into the original position on the hose.
3. If the engine block drain plug was removed, perform the following: Apply pipe sealer to the drain plug. Install the drain plug and tighten to 22 N.m (16 lb ft).
4. Lower the vehicle.
5. Using the «J 38185»(ref-478462-S20288722122012061100000) , position the upper radiator hose clamp at the radiator.
6. Remove the upper radiator hose from the radiator.
7. Remove the coolant air bleed hose from the radiator.
8. Place a funnel into the upper radiator hose.
9. Slowly fill the cooling system through the upper radiator hose with a 50/50 coolant mixture until the coolant comes out the coolant air bleed hose. Refer to «Approximate Fluid Capacities»(ref-478438-S27013746372012061100000) .
10. Connect the upper radiator hose to the radiator.
11. Using the «J 38185»(ref-478462-S20288722122012061100000) position the radiator hose clamp into the original position on the hose.
12. Connect the coolant air bleed hose to the radiator.
13. Fill the radiator with coolant through the filler neck.
14. Install the coolant pressure cap.
15. Fill the coolant overflow bottle to the full line.
16. Start the engine.
17. Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
18. Allow the engine to idle for 3 minutes.
19. Shut the engine OFF.
20. Allow the engine to cool.
21. Top off the coolant as necessary.
22. Inspect the concentration of the engine coolant, using the «J 26568»(ref-478473-S06617945892012061100000) .
23. Rinse away any excess coolant from the engine and the engine compartment.
24. Inspect the cooling system for leaks.

1. Install the lower radiator hose and/or drain cock to the radiator.
2. Reposition the lower radiator hose and install quick connect snap ring.
3. If the left and right engine block coolant drain plugs were removed, perform the following: Apply pipe sealer to the drain plugs. Install the drain plugs and tighten to 60 N.m (44 lb ft).
4. Install the engine block coolant heater, if equipped. Refer to «Coolant Heater Replacement (V8 without 6.0L)»(ref-478473-S13751126962012061100000) , «Coolant Heater Replacement (V6)»(ref-478473-S02535834052012061100000) , «Coolant Heater Replacement (Diesel)»(ref-478473-S33947355422012061100000) , «Coolant Heater Replacement (V8)»(ref-478473-S37687437542012061100000) .
5. Lower the vehicle.
6. Slowly fill the cooling system with a 50/50 coolant mixture. Refer to «Approximate Fluid Capacities»(ref-478438-S27013746372012061100000) .
7. Slowly continue filling as the level goes down.
8. Start the engine.
9. Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature. Engine should reach an operating temperature of 90°C (194°F) and the upper radiator hose should be HOT.
10. Continue to run the engine at 2,000-2,500 for 5 more minutes.
11. Slowly add more coolant to the cooling system.
12. Allow the engine to idle for 5 minutes.
13. Slowly add more coolant to the cooling system.
14. Repeat steps #10 & 11.
15. Install radiator cap.
16. Shut the engine OFF.
17. Allow the engine to cool.
18. Top off the coolant as necessary.
19. Inspect the concentration of the engine coolant using the J 26568 Coolant and Battery Tester .
20. Rinse away any excess coolant from the engine and the engine compartment.

Radiator Cleaning

An engine will overheat if the radiator has any of the following conditions

1. Leaks
2. Dirt or obstructions in the core

Use a soft bristle brush and clean hot water or a mild detergent solution in order to clean the outside of the radiator core. A car wash or dishwashing liquid is a suitable detergent.

A common city water hose may also be used in order to clean the outside of the radiator. Remove the nozzle from the hose prior to use in order to prevent damage to the fins.

Use one of the following solutions in order to pressure flush and clean the inside of the core tubes

1. Clean hot water
2. Mild car wash
3. Dishwashing liquid

Use the following steps in order to test the radiator for restrictions

1. Warm the engine.
2. Turn off the engine.
3. Feel the radiator. The radiator should be hot along the left side and warm along the right side. There should be an even temperature rise from right to left. Cold spots in the radiator indicate clogged sections.

Cooling Fan Control

The purpose of the electro-viscous (EV) fan clutch is to maintain powertrain cooling requirements. The engine control module (ECM) monitors the following sensors to regulate the fan speed

1. Engine coolant temperature
2. A/C refrigerant pressure
3. Vehicle speed
4. Intake air temperature
5. Transmission fluid temperature
6. Ambient air temperature
7. Cooling fan speed

The EV cooling fan clutch system enables the engine control module (ECM) to change the speed of the pulley driven cooling fan in relation to the engine speed. Ignition voltage is supplied directly to the fan clutch solenoid valve. The ECM uses two output drivers and a parallel circuit to directly control the EV fan clutch solenoid valve. The ECM controls the solenoid valve by pulse width modulating (PWM) the parallel control circuits to ground, with a solid state device called a driver. The ECM changes the cooling fan speed by increasing or decreasing the solenoid valve ON time, known as duty cycle. As the ECM command increases, so does the ON time of the solenoid. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and allows the fluid in the coupling of the fan clutch to drain back to the storage chamber, reducing fan speed. The rapid modulation of the fan clutch solenoid valve gives the ECM the ability to precisely control the amount of fluid that remains in the fluid coupler, allowing more effective regulation of the fan speed and powertrain cooling requirements.

The fan clutch supplies a feedback signal to the ECM, as an actual fan speed input. The fan speed sensor is a hall effect sensor which is internal to the fan clutch. The ECM supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.

The scan tool can operate the cooling fan clutch. This is done through the controls function menu screen. Cooling fan clutch engagement can take up to 2 minutes with a 100 percent command and the engine speed at 2,000 RPM. The lower the engine speed, the longer it will take for the fan to engage. Cooling fan disengagement can take up to 2 minutes with the engine speed at 2,000 RPM. The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.

Under certain conditions the cooling fan may be engaged at engine start. The cooling may have been engaged at the time the engine was turned off. Or, fluid may bleed from the storage chamber into the fluid coupling of the cooling fan clutch while the engine is off. Although the fan clutch is commanded off during a cold start, this is the most likely time a vehicle driver will notice that the fan noise is excessive in comparison to engine starts when the fan clutch is disengaged.

Coolant Heater

The optional engine coolant heater (RPO KO5) is designed to warm the coolant in the engine block area for improved starting in very cold weather (temperatures below -29°C (-20°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The engine coolant heater operates using AC external power and a heating element installed in the water jacket of the engine block. The heating element warms the coolant when the heater cord is plugged into an AC power source.

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 systems 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.

Coolant Level Control

The engine cooling system contains an engine coolant level switch which alerts the driver in the event of a coolant loss. When the engine coolant level switch reads a low coolant level in the surge tank, the switch opens. This sends a coolant loss signal to the instrument panel cluster (IPC) by the coolant level switch signal circuit. Ground is provided for the coolant level control.

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 it 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 it absorbs additional heat.

Some engine applications, coolant is also directed to the throttle body. There it circulates through passages in the casting. The coolant assists in regulating the throttle body temperature.

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 operating temperature or it will flow through the thermostat and into the radiator where it 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. It consists of a core and 2 tanks. The aluminum core is a tube and fin cross-flow 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.

The radiator removes heat from the coolant passing through it. The fins on the core transfer heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.

During vehicle use, the coolant is heated and expands. The increased coolant volume flows into the surge tank. As the coolant circulates, any air is allowed to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.

Coolant Recovery System

The coolant recovery system consists of a plastic coolant recovery reservoir, an overflow tube, and a pressure cap on the radiator. The recovery reservoir is also called a recovery tank or expansion tank. It 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 in the cooling system gets too high, it will open the pressure valve in the pressure cap. This allows the coolant, which has expanded due to being heated, 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 that it eliminates almost all air bubbles from the cooling system. Coolant without air bubbles absorbs heat much better than coolant with bubbles.

Pressure Cap

The pressure cap seals the cooling system. It contains a blow off or pressure relief valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring, which protects the radiator from excessive cooling system pressure. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator and/or coolant hoses to collapse.

The pressure cap allows cooling system pressure to build up as the temperature increases. As the pressure builds, the boiling point of the coolant increases. 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 is, the faster the heat transfers from the radiator to the cooler, passing air.

The pressure in the cooling system can get too high. When the cooling system pressure exceeds the rating of the pressure cap, it raises the pressure valve, venting the excess pressure.

As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the surge tank. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator and coolant hoses from collapsing.

Cooling Fan and Clutch

The engine cooling fan and clutch are driven by the crankshaft via the drive belt. The cooling fan draws air through the radiator to improve the transfer of heat from the coolant to the atmosphere. As the fan blades spin, they pull cool, outside air past the radiator core. The fan clutch drives the cooling fan. The fan clutch controls the amount of torque that is transmitted from the crankshaft to the fan blades. The clutch allows more torque to engage on the fan when the engine operating temperature increases and/or the vehicle speed is low. As the torque increases, the fan turns more quickly. The fan clutch decreases the torque applied to the cooling fan when the engine temperature decreases and/or the vehicle speed is high. As the torque decreases, the fan speed decreases.

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, a retaining plate, pulley and an impeller. The impeller is mounted on the pump shaft, and consists of a series of flat or curved blades or vanes on a flat plate. 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. The sealed bearings never need to be lubricated. Grease cannot leak out, dirt and water cannot get in as long as the seal is not damaged or worn.

The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.

Thermostat

The thermostat is a coolant flow control component. It's purpose is to help regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a small piston. When the element is heated, it expands and exerts pressure against a small piston. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.

When the coolant temperature is below 85°C (185°F) for diesel engines and below 91°C (195°F) for gas engines, the thermostat valve remains closed. This prevents circulation of the coolant from the radiator and allows the engine to warm up. After the coolant temperature reaches 85°C (185°F) or 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the engine and then to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.

Engine Oil Cooler

The engine oil cooler is a heat exchanger. It is located inside the left side end tank of the radiator. The engine oil temperature is controlled by the temperature of the engine coolant that surrounds the oil cooler in the radiator.

The engine oil pump pumps the oil through the engine oil cooler line to the oil cooler. The oil then flows through the cooler where the engine coolant absorbs heat from the oil. The oil is then pumped through the oil cooler return line, to the oil filter, to the engine block oil system.

Transmission Oil Cooler

The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant in the radiator.

The transmission oil pump, pumps the fluid through the transmission oil cooler line to the transmission oil cooler. The fluid then flows through the cooler where the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.