Engine Cooling System: Other GMC Savana H1500

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Idle the engine.
2. Command the Cooling Fan Clutch to 10 percent.
3. Operate the engine at 1,500 RPM for 2 minutes. The fan should be quiet to indicate the clutch is disengaged.
4. Command the Cooling Fan Clutch to 80 percent.
5. Operate the engine at 1,500 RPM for 2 minutes. The fan should be loud to indicate the clutch is engaged.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-302123-S03900721962008102100000)
2. «Control Module References»(ref-302118-S20112801552008102100000) for ECM replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

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 cracked drive belt A loose or a worn drive belt A misrouted drive belt Oil leaks at the cooling fan clutch A free-spinning cooling fan A seized cooling fan clutch A broken cooling fan
2. Idle the engine.
3. Command the cooling fan clutch to 10 percent.
4. Operate the engine at 1,500 RPM for 2 minutes. The fan should be quiet to indicate the clutch is disengaged.
5. Command the cooling fan clutch to 80 percent.
6. Operate the engine at 1,500 RPM for 2 minutes. The difference between the fan speed and the desired fan speed should remain less than 1,000 RPM throughout the speed transition.

Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-302123-S03900721962008102100000)
2. «Control Module References»(ref-302118-S20112801552008102100000) for replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Engine OFF, verify the fan clutch is not binding by turning the fan by hand.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-302123-S03900721962008102100000)
2. «Control Module References»(ref-302118-S20112801552008102100000) for ECM replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Idle the engine.
2. Command the cooling fan clutch to 10 percent.
3. Operate the engine at 2,000 RPM for 2 minutes. The fan should be quiet to indicate the clutch is disengaged.
4. Command the cooling fan clutch to 80 percent.
5. Operate the engine at 2,000 RPM for 2 minutes. The difference between the Fan Speed and the Desired Fan Speed should remain less than 1,000 RPM throughout the speed transition.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fan Clutch Replacement»(ref-302123-S03900721962008102100000)
2. «Control Module References»(ref-302118-S20112801552008102100000) for ECM replacement, setup, and programming

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

The low coolant indicator should be OFF with the engine coolant at the proper level.

1. «Instrument Cluster Replacement»(ref-302112-S03808427892008102100000)
2. «Radiator Surge Tank Replacement»(ref-302123-S38725540782008102100000)
3. «Control Module References»(ref-302118-S20112801552008102100000) for ECM replacement, setup, and programming

Repair Verification

Verify that the low coolant indicator is OFF with the engine coolant at the proper level.

Engine Overheating

Loss of Coolant

Tools Required

J 24731 Tempil Stick. See Special Tools .

Use one of the following procedures in testing for a malfunctioning thermostat.

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (4.3L)»(ref-302123-S26406223212008102100000) or «Coolant Heater Replacement (4.8L, 5.3L (except RPO L33), 6.0L)»(ref-302123-S00896068442008102100000) or «Coolant Heater Replacement (6.6L)»(ref-302123-S27694187432008102100000)
2. «Coolant Heater Cord Replacement (4.3L Engine)»(ref-302123-S16573309362008102100000) or «Coolant Heater Cord Replacement (4.8L, 5.3L And 6.0L Engine)»(ref-302123-S15764249982008102100000) or «Coolant Heater Cord Replacement (6.6L Engine)»(ref-302123-S23583763092008102100000)

Electrical Information Reference

1. «Circuit Testing»(ref-302132-S22107311252008102100000)
2. «Connector Repairs»(ref-302132-S18253991032008102100000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-302132-S40146669752008102100000)
4. «Wiring Repairs»(ref-302132-S42054099512008102100000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (4.3L)»(ref-302123-S26406223212008102100000) or «Coolant Heater Replacement (4.8L, 5.3L (except RPO L33), 6.0L)»(ref-302123-S00896068442008102100000) or «Coolant Heater Replacement (6.6L)»(ref-302123-S27694187432008102100000)
2. «Coolant Heater Cord Replacement (4.3L Engine)»(ref-302123-S16573309362008102100000) or «Coolant Heater Cord Replacement (4.8L, 5.3L And 6.0L Engine)»(ref-302123-S15764249982008102100000) or «Coolant Heater Cord Replacement (6.6L Engine)»(ref-302123-S23583763092008102100000)

Procedure

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the J 24460-01 (1) with J 42401 (2) in order to test the pressure cap. See «Special Tools»(ref-302123-S18057185742008102100000) .
4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap. See «Special Tools»(ref-302123-S18057185742008102100000) . Maintain the rated pressure for at least 10 seconds. Note the rate of pressure loss.
5. Replace the pressure cap under the following conditions: The pressure cap does not release pressure which exceeds the rated pressure of the cap. The pressure cap does not hold the rated pressure.

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-302123-S20455861972008102100000) .
3. Wash the pressure cap mating surface with water.
4. Install the J 42401 to the surge tank. See «Special Tools»(ref-302123-S18057185742008102100000) .
5. Use the J 24460-01 in order to apply pressure to the cooling system. See «Special Tools»(ref-302123-S18057185742008102100000) . Do not exceed the pressure cap rating.
6. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gage for any pressure loss.
7. Repair any leaks as required.

Looseness

If the fan assembly is loose, inspect the fan assembly for wear. Replace the fan assembly as necessary.

Observe the tip of the fan blade for lateral movement. Lateral movement occurs under various temperature conditions. A lateral movement measuring 6.5 mm (1/4 in) is normal. This amount of movement is not cause for replacement of the assembly.

Note. Check for adequate clearance between the fan blades and the thermometer sensor before starting the engine, as damage could occur.

Use the following procedure in order to diagnose the causes of engine overheating

1. Ensure that the engine is cool. This will allow complete disengagement of the fan clutch.
2. Spin the fan and clutch assembly by hand. If the fan and clutch assembly easily revolves more than 5 times with no drag, replace the fan clutch.
3. If the fan clutch performs correctly but exhibits drag, position a thermometer between the fan blades and the radiator. Use any of the following methods in order to position the thermometer: Insert the thermometer sensor through one of the existing holes in the fan shroud. Place the thermometer between the radiator and the shroud. On models that do not have holes in the fan shroud, drill a 5 mm (3/16 in) hole in the fan shroud. Insert the thermometer in the hole.
4. Cover the radiator in order to induce a high engine temperature.
5. Start the engine.
6. Turn on the air conditioning.
7. Operate the engine at 2,000 RPM.
8. Wait for 5 to 10 minutes while the temperature increases sufficiently to allow the fan clutch to engage. The following conditions indicate that the fan clutch has engaged: A roaring noise or an increase in fan noise occurs. The thermometer reading drops approximately 3-10°C (5-15°F).
9. Observe the thermometer reading when the fan clutch engages. The following conditions are cause for replacement of the fan clutch: The fan clutch does not engage while the temperature measures 65-90°C (150-195°F). If the fan clutch does not engage while the temperature is within this range, verify that the fan clutch was disengaged at the beginning of the test. Both of the following conditions exist: No temperature drop occurs The fan noise level is constant from the beginning of the test until the time when the engine temperature reaches 88°C (190°F). Do not continue the test past a thermometer reading of 88°C (190°F) in order to prevent overheating.
10. Perform the following steps as soon as the fan clutch engages: Remove the radiator cover. Turn OFF the air conditioning. Operate the engine at approximately 1,500 RPM until the coolant returns to the normal operating temperature.
11. Observe the operation of the fan clutch. The fan clutch should disengage after several minutes. Disengagement of the fan clutch is indicated by a decrease in fan noise or roar. If the fan clutch does not disengage after several minutes, the fan clutch should be replaced.

1. J 26568 Coolant and Battery Tester. See «Special Tools»(ref-302123-S18057185742008102100000) .
2. J 38185 Hose Clamp Pliers. See «Special Tools»(ref-302123-S18057185742008102100000) .

Filling Procedure

1. Connect the lower radiator hose.
2. Using the J 38185 position the clamp into the original position on the hose. See «Special Tools»(ref-302123-S18057185742008102100000) .
3. If the engine block drain plug was removed, perform the following: Apply pipe sealer to the drain plug. Install the drain plug. Tighten: Tighten the drain plug to 22 N.m (16 lb ft).
4. Lower the vehicle.
5. Using the J 38185 , position the upper radiator hose clamp at the radiator. See «Special Tools»(ref-302123-S18057185742008102100000) .
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-302187-S41930729832008102100000) .
10. Connect the upper radiator hose to the radiator.
11. Using the J 38185 position the radiator hose clamp into the original position on the hose. See «Special Tools»(ref-302123-S18057185742008102100000) .
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 . See «Special Tools»(ref-302123-S18057185742008102100000) .
23. Rinse away any excess coolant from the engine and the engine compartment.
24. Inspect the cooling system for leaks.

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.

1. Drain the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(ref-302123-S21188972162008102100000) or «Cooling System Draining and Filling (Vac N Fill)»(ref-302123-S36766816792008102100000) .
2. Recover the refrigerant. Refer to «Refrigerant Recovery and Recharging»(ref-302117-S42569186822008102100000) .
3. Disconnect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(ref-302110-S31613757582008102100000) .
4. Remove the air cleaner assembly. Refer to «Air Cleaner Assembly Replacement»(ref-302156-S30515258882008102100000) .
5. Remove the surge tank. Refer to «Radiator Surge Tank Replacement»(ref-302123-S38725540782008102100000) .
6. Remove the front grille. Refer to «Grille Replacement (Base)»(ref-302101-S05854383762008102100000) or «Grille Replacement (Uplevel)»(ref-302101-S41766073112008102100000) .
7. Remove the front bumper. Refer to «Front Bumper Replacement»(ref-302122-S18475859932008102100000) .
8. Remove the charge air cooler inlet and outlet ducts. Refer to «Charged Air Cooler Hoses/Pipes Replacement (Inlet)»(ref-302188-S31690083802008102100000) or «Charged Air Cooler Hoses/Pipes Replacement (Outlet)»(ref-302188-S42899144452008102100000) .
9. Using the J 38185 , reposition the radiator inlet hose clamp. See «Special Tools»(ref-302123-S18057185742008102100000) .
10. Disconnect the radiator inlet hose from the thermostat housing.
11. Raise and suitably support the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-302124-S03826668542008102100000) .
12. Remove the radiator outlet hose to radiator retaining clip and disconnect the hose.
13. Remove the upper transmission cooler line to radiator retaining clip and disconnect the line.
14. Remove the transmission cooler line to auxiliary transmission cooler retaining clip and disconnect the line.
15. Remove the evaporator to condenser hose retaining nut (1).
16. Disconnect the evaporator to condenser hose from the condenser.
17. Remove the suction hose bolt (1) from the air conditioning (A/C) compressor.
18. Disconnect the suction hose (4) from the A/C compressor.
19. Disconnect the wiring ground located at the RH fender.
20. Remove the RH fender to core support brace bolts and remove the brace.
21. Disconnect the wiring ground located at the LH fender.
22. Remove the LH fender to core support brace bolts and remove the brace.
23. Disconnect the wiring harness electrical connector at the underhood bused electrical center (UBEC).
24. Disconnect the hood release cable at the hood release latch. Position the cable aside.
25. Remove the positive battery cable nut from the junction block and disconnect the cable.
26. Remove the auxiliary positive cable nut from the junction block and disconnect the cable.
27. Remove the positive battery to UBEC cable nut from the junction block and disconnect the cable.
28. Remove the 4 LH and 4 RH core support bolts (1).
29. Remove the core support and the cooling layer.

1. Position the core support and the cooling layer to the vehicle.
2. Install the 4 LH and RH core support bolts (1). Tighten: Tighten the core support bolts to 25 N.m (18 lb ft).
3. Position the positive battery to underhood bused electrical center (UBEC) cable to the junction block and install the nut. Tighten: Tighten the positive battery cable to junction block bolt to 8 N.m (71 lb in).
4. Position the auxiliary positive cable to the junction block and install the nut. Tighten: Tighten the auxiliary positive battery cable to junction block bolt to 8 N.m (71 lb in).
5. Position the positive battery cable to the junction block and install the nut. Tighten: Tighten the positive battery cable to junction block bolt to 8 N.m (71 lb in).
6. Reposition and connect the hood release cable to the hood release latch.
7. Connect the wiring harness electrical connector at the UBEC.
8. Position the LH fender to core support brace and install the bolts.
9. Position the wiring ground to the LH fender and install the bolt. Tighten: Tighten the ground bolt to 9 N.m (80 lb in).
10. Position the RH fender to core support brace and install the bolts.
11. Position the wiring ground to the RH fender and install the bolt. Tighten: Tighten the ground bolt to 9 N.m (80 lb in).
12. Connect the suction hose (4) to the air conditioning (A/C) compressor.
13. Install the suction hose bolt (1) to the A/C compressor. Tighten: Tighten the suction hose bolt to 16 N.m (12 lb ft).
14. Position the evaporator to condenser hose to the condenser.
15. Install the evaporator to condenser hose nut (1). Tighten: Tighten the evaporator to condenser nut to 16 N.m (12 lb ft).
16. Position the transmission cooler line to the auxiliary transmission cooler and install the retaining clip.
17. Position the upper transmission cooler line to the radiator and install the retaining clip.
18. Lower the vehicle.
19. Position the radiator outlet hose to radiator and install the retaining clip.
20. Connect the radiator inlet hose to the radiator.
21. Using the J 38185 , reposition the radiator inlet hose clamp. See «Special Tools»(ref-302123-S18057185742008102100000) .
22. Install the charge air cooler inlet and outlet ducts. Refer to «Charged Air Cooler Hoses/Pipes Replacement (Inlet)»(ref-302188-S31690083802008102100000) or «Charged Air Cooler Hoses/Pipes Replacement (Outlet)»(ref-302188-S42899144452008102100000) .
23. Install the front bumper. Refer to «Front Bumper Replacement»(ref-302122-S18475859932008102100000) .
24. Install the front grille. Refer to «Grille Replacement (Base)»(ref-302101-S05854383762008102100000) or «Grille Replacement (Uplevel)»(ref-302101-S41766073112008102100000) .
25. Install the surge tank. Refer to «Radiator Surge Tank Replacement»(ref-302123-S38725540782008102100000) .
26. Install the air cleaner assembly. Refer to «Air Cleaner Assembly Replacement»(ref-302156-S30515258882008102100000) .
27. Connect the negative battery cable. Refer to «Battery Negative Cable Disconnection and Connection»(ref-302110-S31613757582008102100000) .
28. Recharge the refrigerant. Refer to «Refrigerant Recovery and Recharging»(ref-302117-S42569186822008102100000) .
29. Fill the cooling system. Refer to «Cooling System Draining and Filling (Static Fill)»(ref-302123-S21188972162008102100000) or «Cooling System Draining and Filling (Vac N Fill)»(ref-302123-S36766816792008102100000) .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 41240 Fan Clutch Remover and Installer. See Special Tools .

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 sensor
2. A/C refrigerant pressure sensor
3. Vehicle speed sensor
4. Intake air temperature sensor
5. Transmission fluid temperature sensor
6. Ambient air temperature sensor

The ECM controls the EV fan clutch engagement. The ECM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. 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 blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.

The fan has the ability to create a feedback signal, so the ECM has an actual fan speed input. This is done with a hall effect sensor 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 engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100 percent command with the engine at 2,000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine 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 restart. They are as follows

1. The cooling fan was engaged at the time the engine was turned off.
2. The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan.

Although the fan is commanded off at this time due to a cold start condition. This is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.

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.