Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Low Engine Coolant Indicator Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Connector End View Reference: DEFINITION: The check coolant level display is always on when the key is in the ON position. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. With a scan tool, observe the low coolant switch parameter in the climate control panel HVAC system data list. Does the low coolant switch display open? | Go to Step 3 | Go to |
| 3 | Disconnect the coolant level switch connector. Connect a 3-amp fused jumper wire between the coolant level switch signal circuit and the coolant level switch ground circuit, at the harness connector of the coolant level switch. Does the low coolant switch display closed on the scan tool? | Go to Step 7 | Go to Step 4 |
| 4 | Connect a 3-amp fused jumper wire from the coolant level switch signal circuit at the coolant level switch harness connector to a good ground. Does the low coolant switch display closed on the scan tool? | Go to Step 6 | Go to Step 5 |
| 5 | Test the signal circuit of the coolant level switch for an open. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 8 |
| 6 | Repair the open or high resistance in the coolant level switch ground circuit. Refer to in Wiring Systems. Did you complete the repair? | Go to Step 11 | |
| 7 | Inspect for poor connections at the harness connector of the coolant level switch. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 8 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 9 | Replace the coolant level switch. Did you complete the replacement? | Go to Step 11 | |
| 10 | Replace the HVAC control module. Refer to in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | Go to Step 11 | |
| 11 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Low Engine Coolant Indicator Always On
Cooling Fan Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: One or both engine cooling fan motors run continuously in high or low speed. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Are both cooling fans operating at low speed? | Go to Step 4 | Go to Step 3 |
| 3 | Is the left cooling fan operating at high speed? | Go to Step 5 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 4 | Remove the low speed fan relay. Did the fans turn OFF? | Go to Step 8 | Go to Step 6 |
| 5 | Remove the high speed fan relay. Did the left cooling fan turn OFF? | Go to Step 9 | Go to Step 7 |
| 6 | Repair the cooling fan motor supply voltage circuit of the right cooling fan for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | |
| 7 | Repair the cooling fan motor supply voltage circuit of the left cooling fan for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | |
| 8 | Inspect for poor connections at the low speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
| 9 | Inspect for poor connections at the high speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
| 10 | Replace the low speed fan relay. Did you complete the replacement? | Go to Step 12 | |
| 11 | Replace the high speed fan relay. Did you complete the replacement? | Go to Step 12 | |
| 12 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Cooling Fan Always On
Cooling Fan Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: One or both cooling fan motors are inoperative in either high, low, or both speeds. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the Fans Low Speed ON and OFF. Do the low speed engine cooling fans turn ON and OFF with each command? | Go to Step 3 | Go to Step 4 |
| 3 | IMPORTANT: A 3-second delay occurs before the powertrain control module (PCM) changes the cooling fan speed. With a scan tool, command the Fans High Speed ON and OFF.Do the high speed engine cooling fans turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 6 |
| 4 | IMPORTANT: Do NOT remove the jumper wire that you will be connecting until your testing is completed. If the low speed fan fuse opens when you connect the jumper wire, repair the cooling fan motor supply voltage circuit of the right cooling fan motor for a short to ground. Disconnect the low speed fan relay. Connect a jumper wire between the battery positive voltage circuit and the cooling fan motor supply voltage circuit of the low speed fan relay. Do both cooling fans operate in low speed? | Go to Step 14 | Go to Step 5 |
| 5 | Disconnect the S/P fan relay. With a test lamp connected to a good ground, probe the cooling fan low reference circuit at the S/P fan relay. Does the test lamp illuminate? | Go to Step 9 | Go to Step 8 |
| 6 | Does the right cooling fan operate at high speed? | Go to Step 16 | Go to Step 7 |
| 7 | Inspect the ground circuit of the S/P fan relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 15 |
| 8 | Install the S/P fan relay. Disconnect the right cooling fan electrical connector. With a test lamp connected to a good ground, probe the cooling fan motor supply voltage circuit at the right cooling fan motor connector. Does the test lamp illuminate? | Go to Step 12 | Go to Step 13 |
| 9 | Install the S/P fan relay. Disconnect the left cooling fan motor connector. With a test lamp connected to a good ground, probe the cooling fan motor supply voltage circuit at the left cooling fan connector. Does the test lamp illuminate? | Go to Step 11 | Go to Step 10 |
| 10 | Inspect the cooling fan motor supply voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 15 |
| 11 | Inspect the ground circuit of the left cooling fan for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 18 |
| 12 | Inspect the cooling fan low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 17 |
| 13 | Inspect the cooling fan motor supply voltage circuit of the right cooling fan for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 19 |
| 14 | Inspect for poor connections at the low speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 20 |
| 15 | Inspect for poor connections at the S/P fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 21 |
| 16 | Inspect for poor connections at the high speed fan relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 22 |
| 17 | Inspect for poor connections at the harness connector of the right cooling fan. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 |
| 18 | Inspect for poor connections at the harness connector of the left cooling fan. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 24 |
| 19 | Repair the battery positive voltage circuit for an open or high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 25 | |
| 20 | Replace the low speed fan relay. Did you complete the replacement? | Go to Step 25 | |
| 21 | Replace the S/P fan relay. Did you complete the replacement? | Go to Step 25 | |
| 22 | Replace the high speed fan relay. Did you complete the replacement? | Go to Step 25 | |
| 23 | Replace the right cooling fan. Refer to Cooling Fan Replacement - Electric (LH2 Standard Cooling) or Cooling Fan Replacement - Electric (LH2 Heavy Duty Cooling) or Cooling Fan Replacement - Electric (LY7) . Did you complete the replacement? | Go to Step 25 | |
| 24 | Replace the left cooling fan. Refer to Cooling Fan Replacement - Electric (LH2 Standard Cooling) or Cooling Fan Replacement - Electric (LH2 Heavy Duty Cooling) or Cooling Fan Replacement - Electric (LY7) . Did you complete the replacement? | Go to Step 25 | |
| 25 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| A 3-second delay occurs before the powertrain control module (PCM) changes the cooling fan speed. |
| IMPORTANT |
|---|
| Do NOT remove the jumper wire that you will be connecting until your testing is completed. If the low speed fan fuse opens when you connect the jumper wire, repair the cooling fan motor supply voltage circuit of the right cooling fan motor for a short to ground. |
Cooling Fan Inoperative
After Boil Coolant Pump Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The after-boil coolant pump does not operate under certain conditions. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the Water Pump Control ON in climate control panel (CCP) special functions, miscellaneous test. Does the after-boil coolant pump operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Disconnect the after-boil relay. Connect a test lamp between the control circuit of the after-boil relay and the coil supply voltage circuit of the after-boil relay. With a scan tool command the Water Pump Control ON and OFF. Does the test lamp illuminate? | Go to Step 4 | Go to Step 5 |
| 4 | Connect a 5-amp fused jumper wire between the battery positive voltage circuit of the after-boil relay and the after-boil coolant pump supply voltage circuit of the after-boil relay. Does the after-boil coolant pump operate? | Go to Step 12 | Go to Step 8 |
| 5 | Test the control circuit of the after-boil relay for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 6 |
| 6 | Test the battery positive voltage circuit of the after-boil relay for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 7 |
| 7 | Test the voltage supply circuit of the after-boil coolant pump for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 10 |
| 8 | Test the voltage supply circuit of the after-boil coolant pump for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
| 9 | Test the ground circuit of the after-boil coolant pump for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
| 10 | Replace the HVAC Control Module. Refer to HVAC Control Module Replacement in HVAC Systems - Automatic. Did you complete the replacement? | Go to Step 13 | |
| 11 | Replace the after-boil coolant pump. Refer to Afterboil Coolant Pump Replacement . Did you complete the replacement? | Go to Step 13 | |
| 12 | Replace the after-boil relay. Did you complete the replacement? | Go to Step 13 | |
| 13 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
After Boil Coolant Pump Inoperative
Loss of Coolant
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: The cooling system is loosing coolant either internally or externally. | |||
| 1 | Were you sent here from Symptoms or another diagnostic table? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Repair any present DTCs. Refer to Diagnostic Starting Point - Engine Cooling . Is the action complete? | Go to Step 3 | |
| 3 | Inspect the coolant level. Is the coolant at the proper level? | Go to Step 6 | Go to Step 4 |
| 4 | Fill the cooling system to the proper level. Refer to Draining and Filling Cooling System . 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 cylinder. Does the engine crankshaft rotate? | Go to Step 6 | Go to Step 23 |
| 6 | Engine overheating can cause a loss of coolant. Is the engine overheating? | Go to Step 24 | Go to Step 7 |
| 7 | Extended engine operation with a low coolant level can cause engine internal component failure. Is the engine knocking? | Go to Step 26 | 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 25 | Go to Step 10 |
| 10 | 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: Afterboil pump Engine Heater Radiator Surge tank Are any of the hoses, clamps or pipes leaking? | Go to Step 19 | Go to Step 12 |
| 12 | Visually inspect the following components: Core plugs Cylinder head gaskets Engine block Intake manifold Radiator Thermostat Water pump Surge tank Surge tank cap Are any of the listed components leaking? | Go to Step 19 | Go to Step 13 |
| 13 | Pressure test the cooling system. Refer to Cooling System Leak Testing . Visually inspect the components listed in steps 11 and 12 again. Are any leaks present? | Go to Step 19 | 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 20 |
| 15 | Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure? | Go to Step 27 | Go to Step 20 |
| 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 under the HVAC module Is coolant present? | Go to Step 21 | Go to Step 17 |
| 17 | Inspect the underside of the oil fill cap for a gray/white milky substance. Is there a milky substance under the oil fill cap? | Go to Step 18 | Go to Step 28 |
| 18 | Inspect the engine oil fluid level indicator for a gray/white milky substance. Is there a milky substance on the engine oil fluid level indicator? | Go to Step 25 | Go to Step 28 |
| 19 | Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete? | Go to Step 28 | |
| 20 | Replace the coolant pressure cap. Is the repair complete? | Go to Step 28 | |
| 21 | Replace the heater core. Refer to Heater Core Replacement in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 28 | |
| 22 | Replace the radiator. Refer to Radiator Replacement (LH2 Standard Cooling) or Radiator Replacement (LH2 Heavy Duty Cooling) or Radiator Replacement (LY7 Standard Cooling) . Is the repair complete? | Go to Step 28 | |
| 23 | Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate in Engine Mechanical - 4.6L (LH2) or Engine Will Not Crank - Crankshaft Will Not Rotate in Engine Mechanical - 3.6L (LY7). Is the repair complete? | Go to Step 28 | |
| 24 | Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete? | Go to Step 28 | |
| 25 | Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber or Coolant in Engine Oil in Engine Mechanical - 4.6L (LH2) or Coolant in Combustion Chamber or Coolant in Engine Oil in Engine Mechanical - 3.6L (LY7). Is the repair complete? | Go to Step 28 | |
| 26 | Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed in Engine Mechanical - 4.6L (LH2) or Lower Engine Noise, Regardless of Engine Speed in Engine Mechanical - 3.6L (LY7). Is the repair complete? | Go to Step 28 | |
| 27 | Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test in Engine Mechanical - 4.6L (LH2) or Cylinder Leakage Test in Engine Mechanical - 3.6L (LY7). Is the repair complete? | Go to Step 28 | |
| 28 | Operate the system in order to verify the repair. Did you find and correct the condition? | System OK | Go to Step 2 |
Loss of Coolant
Tools Required
J 24731 Tempilstick. See Special Tools .
The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the outlet coolant pipe, located between the thermostat housing and the inlet radiator hose.
- Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat. J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F). J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).
- Replace the coolant thermostat if it does not operate properly between this temperature range.
Coolant Heater Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: The coolant heater does not warm the engine coolant properly. | |||
| 1 | Did you perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Test the engine coolant heater power supply cord for an open or short to ground. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | Go to Step 3 | Go to Step 4 |
| 3 | Replace the engine coolant heater power supply cord. Refer to Coolant Heater Cord Replacement (LH2 (K05,KA3)) or Coolant Heater Cord Replacement (LY7 (KO5)) . Did you complete the replacement? | Go to Step 6 | |
| 4 | Inspect for poor connections at the harness connector of the engine coolant heater. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
| 5 | Replace the engine coolant heater. Refer to Coolant Heater Replacement (LH2 (KO5)) or Coolant Heater Replacement (LH2 (KA3)) or Coolant Heater Replacement (LY7, KO5) . Did you complete the replacement? | Go to Step 6 | |
| 6 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Coolant Heater Inoperative
J 26568 Coolant and Battery Fluid Tester. See Special Tools .
Fill Procedure
- Close the radiator drain cock.
- Install the air deflector. Refer to «Air Deflector Replacement - Front»(ref-197566-S09922059352005101200000) .
- Lower the vehicle.
- Slowly add a mixture of 50/50 DEX-COOL antifreeze and clean drinkable water to the cooling system through the top of the surge tank opening. Refer to «Capacities - Approximate Fluid»(ref-197595-S36803739682005101200000) .
- Slowly fill the cooling system until the coolant stabilizes at 25 mm (1 inch) above the FULL COLD mark on the surge tank.
- Install the surge tank cap.
- Start the engine.
- Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
- Allow the engine to idle for 3 minutes.
- Shut the engine OFF.
- Allow the engine to cool.
- Add or remove coolant as necessary from the surge tank until the level is stabilized at the FULL COLD mark.
- Inspect the cooling system for leaks.
- Using J 26568 inspect the concentration of the engine coolant. See «Special Tools»(ref-197587-S04508623182005101200000) .
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.
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 41240 Fan Clutch Remove and Installer. See Special Tools .
J 41240 Fan Clutch Wrench. See Special Tools .
EN 46104 Water Pump Pulley Holding Tool
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 puller type electrical cooling fans and 3 fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the 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 G104.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan 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 ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the high speed fan relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan S/P relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the high speed fan relay coil is energized closing the relay contacts, and provides battery positive voltage from the high fan 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 ECM commands the low speed cooling fans ON under the following conditions
- Engine coolant temperature exceeds approximately 94.5°C (202°F).
- A/C refrigerant pressure exceeds 1447 kPa (210 psi).
- After the vehicle is shut OFF, if the engine coolant temperature at key-off is greater than 101°C (214°F), the low speed fans will run for a minimum of 60 seconds. After 60 seconds, if the coolant temperature drops below 101°C (214°F), the fans will shut OFF. The fans will automatically shut OFF after 3 minutes, regardless of coolant temperature.
The ECM commands the high speed fans ON under the following conditions
- Engine coolant temperature exceeds approximately 104.25°C (220°F).
- A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
- When certain DTCs set
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed, if required. This ensures idle stability by preventing the fans from cycling between high and low speed.
Cooling Fan Control - Three Fan System
The engine cooling fan system consists of a mechanical fan, 2 electrical pusher-type cooling fans, and 3 fan relays. The low speed, high speed, and series parallel (S/P) relays are arranged in an S/P configuration that allows the engine control module (ECM) to operate the left cooling fan and right cooling fan 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 G104.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan 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 ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the high speed fan relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan S/P relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the high speed fan relay coil is energized closing the relay contacts, and provides battery positive voltage from the high fan 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 ECM commands the low speed fans ON under the following conditions
- Engine coolant temperature exceeds approximately 94.5°C (202°F).
- A/C refrigerant pressure exceeds 1447 kPa (210 psi).
- After the vehicle is shut OFF, if the engine coolant temperature at key-off is greater than 101°C (214°F), the low speed fans will run for a minimum of 60 seconds. After 60 seconds, if the coolant temperature drops below 101°C (214°F), the fans will shut OFF. The fans will automatically shut OFF after 4 minutes, regardless of coolant temperature.
The ECM commands the high speed fans ON under the following conditions
- Engine coolant temperature exceeds approximately 104.25°C (220°F).
- A/C refrigerant pressure exceeds 1824 kPa (265 psi).
- When certain DTCs set
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed, if required. This ensures idle stability by preventing the fans from cycling between high and low speed.
Engine Coolant
Engine coolant is the key element of the heating system. The engine thermostat controls the normal engine operating coolant temperature. Coolant pumped out of the engine block enters the heater core through the inlet heater hose. The air flowing through the HVAC module absorbs the heat of the coolant flowing through the heater core. The coolant then exits the heater core through the heater outlet hose. To prevent the coolant from boiling after the engine is turned OFF an after-boil/heater coolant pump is used.
The HVAC control module will command the after-boil/heater coolant pump ON, when the engine is OFF, under the following conditions
- The engine is OFF.
- The engine coolant temperature is above 101°C (214°F).
The above coolant flow circuits are designed to show the coolant flow related to the coolant by-pass valve positions only. The thermostat function and thermostat coolant flow paths are not shown.
Coolant Warning Messages
The radio will display the following messages if the following conditions exist in the cooling system.
- Engine hot - A/C OFF will be displayed if coolant temperature is above 117°C (243°F). For imports 115°C (239°F).
- Engine coolant hot-Idle engine will be displayed if coolant temperature is above 118°C (245°F).
- Engine overheated-Stop engine will be displayed if coolant temperature is above 123°C (253°F).
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 HVAC control module detects an open, or a high voltage level on the coolant level indicator control circuit for at least 10 seconds, it will send a class 2 message to the radio requesting display of the low coolant level message. There is approximately a 10 second delay before the HVAC control module sends a class 2 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 110-volt 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 maintains an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system removes approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the system cools slowly or not at all, allowing the engine to warm quickly.
Cooling Cycle
The thermostat is located between the radiator outlet and the water pump inlet. At normal operating temperature, coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. In cold conditions, the thermostat bypasses the radiator, and the pump draws coolant directly from the engine outlet.
Coolant is then pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders and absorbs heat.
The coolant is then forced 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, absorbing 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. During normal operating temperatures, the coolant assists in keeping the throttle body cool.
From the cylinder heads, the coolant is then forced to the engine outlet. Coolant leaves the engine through 4 different routes
- Through the engine outlet fitting to the radiator. This path is blocked at cold conditions by the thermostat at the engine inlet fitting.
- Through the radiator bypass
- To the heater core for passenger compartment heat and defrost
- Through the vent hose to the surge tank, providing continuous de-aeration of the cooling system
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 clean drinkable 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 crossflow tube and fin design. This is a brazed tube with convoluted louvered fin design. Separate tubes and fins are stacked together with a manifold at each end. The entire core assembly is then brazed, forming a homogeneous unified structure. The fins allow for efficient heat transfer from the coolant to the atmosphere. The inlet and outlet tanks are molded with a high temperature, glass reinforced nylon plastic. The tank and gasket is supplied as an assembly with silicone gasket attached to the tank. 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 which is located in the bottom of the passenger side tank. The drain cock includes the drain cock and drain cock seal.
The radiator removes heat from the coolant passing through the radiator. The fins on the core absorb heat from the coolant passing through the tubes. Air passing between the fins absorbs heat and cools the coolant.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Pressure Cap
The pressure cap seals and pressurizes the cooling system. The cap contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against the valve seat by a spring which protects the radiator by relieving pressure exceeding 15 psi. The vacuum valve is held against the valve seat by a spring which permits opening of the valve to relieve vacuum created in the cooling system during cooling. The vacuum, if not relieved, could cause the radiator hoses to collapse.
The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant rises as well. Therefore, the coolant can be safely run at a temperature higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler, passing air. However, if the pressure exceeds the strength of the spring, the pressure valve rises so that the excess pressure can escape. When 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 cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, thus preventing the radiator hoses from collapsing.
Surge Tank
The surge tank is a plastic tank with a mounted pressure cap. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system. The air space allows the coolant to expand and contract. The surge tank also provides a coolant fill point and a central air bleed location.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system, because 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 system cooling. Deflectors are installed under the vehicle which redirect airflow beneath the vehicle to flow through the radiator and increase cooling. Air baffles are also used to direct airflow into the radiator and increase cooling. Air seals prevent air from bypassing the radiator and A/C condenser. Air seals also prevent recirculation of the 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 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. 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. Its purpose is to regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a piston. When the element is heated, it expands and exerts pressure against a rubber diaphragm. 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 the rated thermostat opening temperature, 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 rated thermostat opening temperature, 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 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 Heat Exchanger
The engine oil heat exchanger is mounted to the top of the engine block, under the intake manifold flange. Oil is pumped through the oil cooler inlet pipe to the heat exchanger, back through the oil cooler outlet pipe, and then to the oil passages in the engine for lubrication. The exchanger provides the following 2 functions
- Engine coolant warms up faster than the engine oil. During cold operation, the coolant warms the oil and provides better flow during cold engine operation.
- After the engine reaches normal operating temperature, the engine oil temperature will exceed the engine coolant temperature. The coolant flowing through the engine oil cooler will absorb heat from the engine oil. Cooling the engine oil extends oil life and helps reduce internal engine wear.
Transmission Oil Cooler - V09
Note. The transmission oil cooler system uses quick connect fittings throughout the system. Use a special tool to disconnect these quick connect fittings. Removing the transmission oil cooler lines without this tool will result in damage to the radiator, the transmission, and the transmission oil cooler caused by mixing the transmission oil and coolant or due to transmission oil loss.
The transmission oil cooler (TOC) is an oil-to-water heat exchanger located in the radiator end tank and is non-serviceable. The transmission oil temperature is regulated by the temperature of the coolant leaving the radiator. The oil out of the transmission is plumbed through the TOC lines to the radiator end tank cooler then directed back to the transmission.
Transmission Oil Cooler - V03/V92
Note. The transmission oil cooler system uses quick connect fittings throughout the system. Use a special tool to disconnect these quick connect fittings. Removing the transmission oil cooler lines without this tool will result in damage to the radiator, the transmission, and the transmission oil cooler caused by mixing the transmission oil and coolant or due to transmission oil loss.
The transmission oil cooler (TOC) is an oil-to-air heat exchanger located between the radiator and the A/C condenser. The transmission oil temperature is regulated by the airflow passing over this heat exchanger. The oil out of the transmission is plumbed through the TOC lines to the cooler then directed back to the transmission. This cooler helps provided additional cooling for performance driving conditions.
Transmission Oil Cooler Lines
Note. The transmission oil cooler system uses quick connect fittings throughout the system. Use a special tool to disconnect these quick connect fittings. Removing the transmission oil cooler lines without this tool will result in damage to the radiator, the transmission, and the transmission oil cooler caused by mixing the transmission oil and coolant or due to transmission oil loss.
The transmission oil cooler (TOC) lines use quick connect fittings that must be removed using a special tool. The oil out of the transmission is pumped at a high pressure through the TOC lines to the heat exchanger and then directed back to the transmission.
Power Steering Oil Cooler
Some vehicles are equipped with a power steering oil cooler located either between the radiator and condenser (Heavy Duty) or in front of the engine. This cooler transfers heat from the power steering system to the air passing through the condenser and radiator. The cooler uses constant tension clamps on the hose connections to the cooler.