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.
Cooling Fan Always On (Always On in Low Speed)
| Symptom | Causes |
|---|---|
| Fan motor always on in high speed | Short to ground in the fan 2 relay coil control circuits. |
| Fan motor always on in low speed | Short to ground in the fan 1 relay coil control circuit. Short to B+ in the fan motor supply voltage circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan motor is always on in low speed. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Ensure that the ECT is below 93°C (199°F). Depress the A/C switch to the OFF position. Turn the blower switch to the OFF position. Turn the ignition switch to the RUN position. Is the fan motor running continuously? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Remove the fan 1 relay from the underhood fuse block. Is the fan motor running continuously? | Go to Step 4 | Go to Step 5 |
| 4 | Repair the short to voltage in the fan motor supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | |
| 5 | Test the fan 1 relay coil control circuit 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 7 | Go to Step 6 |
| 6 | Replace the fan 1 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 7 | |
| 7 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Cooling Fan Always On (Always On in Low Speed)
Cooling Fan Always On (Always On in High Speed)
| Symptom | Causes |
|---|---|
| Fan motor always on in high speed | Short to ground in the fan 2 relay coil control circuits. |
| Fan motor always on in low speed | Short to ground in the fan 1 relay coil control circuit. Short to B+ in the fan motor supply voltage circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan motor is always on in high speed. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Ensure that the ECT is below 93°C (199°F). Depress the A/C switch to the OFF position. Turn the blower switch to the OFF position. Turn the ignition switch to the RUN position. Is the fan motor running continuously? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Remove the fan 2 relay from the underhood fuse block. Is the fan motor running continuously? | Go to Step 4 | Go to Step 5 |
| 4 | Repair the short to ground in one of the two fan 2 relay coil control circuits. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | |
| 5 | Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement . 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 3 |
Cooling Fan Always On (Always On in High Speed)
Cooling Fan Inoperative (Inoperative in Low Speed)
| Symptom | Causes |
|---|---|
| Fan motor inoperative in both speeds | Open or short to ground in the fan 1 relay supply voltage circuits. Open or short to B+ in the fan 1 relay coil control circuit. Open or short to ground in the fan motor supply voltage circuit. Short to ground in the fan 2 coil supply voltage circuit. Open or short to B+ in the fan motor ground circuit. Short to B+ in the fan 2 coil control circuit. |
| Fan motor inoperative in high speed only | Open in the fan 2 relay supply voltage circuit. Open in the fan 2 relay coil control circuit. Open in the fan 2 relay high speed ground circuit. |
| Fan motor low speed operates at high speed | Short to ground in the fan motor ground circuit. Short to ground in the fan resistor circuit. |
| Fan motor inoperative in low speed only | Open or short to B+ in the fan resistor circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan motor is inoperative in low speed. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Connect a scan tool. The engine must be below operating temperature. Use the scan tool to command the A/C compressor clutch relay ON. When the relay is energized the cooling fan will also run at low speed. Does the cooling fan operate at low speed? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Remove the fan 2 relay. Install a 30 amp fused jumper between the fan motor control circuit and the low speed fan circuit (between cavities 3 and 4) of the cooling fan 2 relay connector. Use the scan tool to command the A/C compressor clutch relay ON. When the relay is energized the cooling fan will also run at low speed. Does the cooling fan operate at low speed? | Go to Step 6 | Go to Step 4 |
| 4 | Test the low speed fan motor ground circuit for an open, or for a short to B+, between the fan 2 relay terminal 4 and S103. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
| 5 | Inspect for a poor connection at the harness connector of the fan resistor. 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 9 | Go to Step 8 |
| 6 | Inspect for a poor connection at the harness connector of the fan 2 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 9 | Go to Step 7 |
| 7 | Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 9 | |
| 8 | Replace the fan resistor. Did you complete the replacement? | Go to Step 9 | |
| 9 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Cooling Fan Inoperative (Inoperative in Low Speed)
Cooling Fan Inoperative (Inoperative in High and Low Speeds)
| Symptom | Causes |
|---|---|
| Fan motor inoperative in both speeds | Open or short to ground in the fan 1 relay supply voltage circuits. Open or short to B+ in the fan 1 relay coil control circuit. Open or short to ground in the fan motor supply voltage circuit. Short to ground in the fan 2 coil supply voltage circuit. Open or short to B+ in the fan motor ground circuit. Short to B+ in the fan 2 coil control circuit. |
| Fan motor inoperative in high speed only | Open in the fan 2 relay supply voltage circuit. Open in the fan 2 relay coil control circuit. Open in the fan 2 relay high speed ground circuit. |
| Fan motor low speed operates at high speed | Short to ground in the fan motor ground circuit. Short to ground in the fan resistor circuit. |
| Fan motor inoperative in low speed only | Open or short to B+ in the fan resistor circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics . Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan motor is inoperative in both fan speeds. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Run the engine until operating temperature is reached and the thermostat opens. Does the cooling fan operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Stop the engine. Disconnect the fan motor connector. Connect a test lamp across the fan motor connector. Start the engine. Does the test lamp illuminate? | Go to Step 11 | Go to Step 4 |
| 4 | Connect the fan motor. Exchange the fan 1 relay with a known good relay (the horn relay). Refer to Cooling Fan Relay Replacement . Does the cooling fan operate? | Go to Step 10 | Go to Step 5 |
| 5 | Test the fan 1 relay and the fan 2 relay supply voltage circuits 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 16 | Go to Step 6 |
| 6 | Test the fan 1 relay coil control circuit for an open or a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 7 |
| 7 | Test the fan 2 relay coil control circuit for a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 8 |
| 8 | Test the fan motor supply voltage circuit 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 16 | Go to Step 9 |
| 9 | Test the fan motor ground circuit for an open or a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 16 | Go to Step 12 |
| 10 | Inspect for a poor connection at the harness connector of the fan 1 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 16 | Go to Step 13 |
| 11 | Inspect for a poor connection at the harness connector of the fan motor. 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 16 | Go to Step 14 |
| 12 | Inspect for a poor connection at the harness connector of the powertrain control module (PCM). 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 16 | Go to Step 15 |
| 13 | Replace the fan 1 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 16 | |
| 14 | Replace the fan motor. Refer to Cooling Fan Replacement - Electric . Did you complete the replacement? | Go to Step 16 | |
| 15 | Replace the PCM. Refer to Powertrain Control Module Programming and Setup in Programming and Setup. Did you complete the replacement? | Go to Step 16 | |
| 16 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Cooling Fan Inoperative (Inoperative in High and Low Speeds)
Cooling Fan Inoperative (Inoperative in High Speed)
| Symptom | Causes |
|---|---|
| Fan motor inoperative in both speeds | Open or short to ground in the fan 1 relay supply voltage circuits. Open or short to B+ in the fan 1 relay coil control circuit. Open or short to ground in the fan motor supply voltage circuit. Short to ground in the fan 2 coil supply voltage circuit. Open or short to B+ in the fan motor ground circuit. Short to B+ in the fan 2 coil control circuit. |
| Fan motor inoperative in high speed only | Open in the fan 2 relay supply voltage circuit. Open in the fan 2 relay coil control circuit. Open in the fan 2 relay high speed ground circuit. |
| Fan motor low speed operates at high speed | Short to ground in the fan motor ground circuit. Short to ground in the fan resistor circuit. |
| Fan motor inoperative in low speed only | Open or short to B+ in the fan resistor circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The engine cooling fan motor is inoperative in high speed. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Run the engine until operating temperature is reached and the thermostat opens. Does the cooling fan operate at high speed? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Test the fan 2 relay coil supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 4 |
| 4 | Test the fan 2 relay coil control circuits for an open or for a short to B+. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 5 |
| 5 | Remove the fan 2 relay. Install a 30 amp fused jumper between the fan motor control circuit and the high speed fan circuit (between cavities 3 and 5) of the fan 2 relay connector. Does the cooling fan operate at high speed? | Go to Step 7 | Go to Step 6 |
| 6 | Test for an open in the fan 2 relay high speed ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 8 |
| 7 | Inspect for a poor connection at the harness connector of the fan 2 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 11 | Go to Step 9 |
| 8 | Inspect for a poor connection at the harness connector of the Powertrain Control Module (PCM). 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 11 | Go to Step 10 |
| 9 | Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 11 | |
| 10 | Replace the PCM. Refer to Powertrain Control Module Programming and Setup in Programming and Setup. Did you complete the replacement? | Go to Step 11 | |
| 11 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
Cooling Fan Inoperative (Inoperative in High Speed)
Cooling Fan Inoperative (Low Speed Operates in High Speed)
| Symptom | Causes |
|---|---|
| Fan motor inoperative in both speeds | Open or short to ground in the fan 1 relay supply voltage circuits. Open or short to B+ in the fan 1 relay coil control circuit. Open or short to ground in the fan motor supply voltage circuit. Short to ground in the fan 2 coil supply voltage circuit. Open or short to B+ in the fan motor ground circuit. Short to B+ in the fan 2 coil control circuit. |
| Fan motor inoperative in high speed only | Open in the fan 2 relay supply voltage circuit. Open in the fan 2 relay coil control circuit. Open in the fan 2 relay high speed ground circuit. |
| Fan motor low speed operates at high speed | Short to ground in the fan motor ground circuit. Short to ground in the fan resistor circuit. |
| Fan motor inoperative in low speed only | Open or short to B+ in the fan resistor circuit. |
Reference Table
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics . Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan motor low speed operates at high speed. | |||
| 1 | Did you review the Cooling System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Connect a scan tool. The engine must be below operating temperature. Use the scan tool to command the A/C compressor clutch relay ON. When the relay is energized the cooling fan will also run at low speed. Does the cooling fan operate at high speed? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Remove the fan 2 relay. Use the scan tool to command the cooling fan ON. Does the cooling fan operate at high speed? | Go to Step 8 | Go to Step 4 |
| 4 | Test the fan 2 relay. The relay should be normally open between terminals 3 and 5 and normally closed between terminals 3 and 4. Did the relay test OK? | Go to Step 5 | Go to Step 9 |
| 5 | Test the fan 2 relay coil control circuits 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 12 | Go to Step 6 |
| 6 | Test the refrigerant pressure switch for a closed condition. The switch should be normally open between terminals 2 and 3. Did the switch test OK? | Go to Step 7 | Go to Step 10 |
| 7 | Inspect for a poor connection at the harness connector of the Powertrain Control Module (PCM). 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 |
| 8 | Repair the short to ground in the fan motor ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | |
| 9 | Replace the fan 2 relay. Refer to Cooling Fan Relay Replacement . Did you complete the replacement? | Go to Step 12 | |
| 10 | Replace the refrigerant pressure switch. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 12 | |
| 11 | Replace the PCM. Refer to Powertrain Control Module Programming and Setup in Programming and Setup. 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 3 |
Cooling Fan Inoperative (Low Speed Operates in High Speed)
Engine Overheating
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Inspect the following conditions: The level of the coolant The mixture of the coolant Is the coolant mixed properly and at the proper level? | Go to Step 3 | Go to Step 2 |
| 2 | Add the coolant. Does the engine still overheat? | Go to Step 3 | System OK |
| 3 | Inspect the generator/coolant pump drive belt. Is the generator/coolant pump drive belt loose or missing? | Go to Step 4 | Go to Step 5 |
| 4 | Adjust or replace the belt. Does the engine still overheat? | Go to Step 5 | System OK |
| 5 | Inspect the front of the radiator for the following items: Dirt Leaves Insects Is the front of the radiator dirty? | Go to Step 6 | Go to Step 7 |
| 6 | Clean the front of the radiator. Does the engine still overheat? | Go to Step 7 | System OK |
| 7 | Inspect the following components for leaks: The hoses The coolant pump The heater The thermostat housing The radiator The head gasket Is leakage present? | Go to Step 8 | Go to Step 9 |
| 8 | Repair the leaks as necessary. Does the engine still overheat? | Go to Step 9 | System OK |
| 9 | Inspect the thermostat. Is the thermostat faulty? | Go to Step 10 | Go to Step 11 |
| 10 | Replace the thermostat. Does the engine still overheat? | Go to Step 11 | System OK |
| 11 | Inspect the cylinder head torque. Is the cylinder head torque correct? | Go to Step 13 | Go to Step 12 |
| 12 | Re-tighten the cylinder head bolts to specification. Replace the cylinder head gasket if required. Does the engine still overheat? | Go to Step 13 | System OK |
| 13 | Inspect the intake manifold. Is the intake manifold leaking? | Go to Step 14 | Go to Step 15 |
| 14 | Complete the following actions as necessary in order to correct the leak: Repair the intake manifold. Replace the components. Does the engine still overheat? | Go to Step 15 | System OK |
| 15 | Inspect the cylinder head gasket. Is the cylinder head gasket leaking? | Go to Step 16 | Go to Step 17 |
| 16 | Repair or replace the components as necessary in order to correct the leak. Does the engine still overheat? | Go to Step 17 | System OK |
| 17 | Inspect the cylinder block plug. Is the cylinder block plug leaking? | Go to Step 18 | Go to Step 19 |
| 18 | Repair or replace the components as necessary in order to correct the leak. Does the engine still overheat? | Go to Step 19 | System OK |
| 19 | Inspect the heater core. Is the heater core leaking? | Go to Step 20 | Go to Step 21 |
| 20 | Repair or replace the components as necessary in order to correct the leak. Does the engine still overheat? | Go to Step 21 | System OK |
| 21 | Inspect the coolant valve, if equipped. Is the coolant valve leaking? | Go to Step 22 | |
| 22 | Repair or replace the components as necessary in order to correct the leak. Does the engine still overheat? | System OK |
Engine Overheating
Loss of Coolant
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Inspect the radiator. Is the radiator leaking? | Go to Step 2 | Go to Step 3 |
| 2 | Repair the radiator as necessary. Is a loss of coolant still evident? | Go to Step 3 | System OK |
| 3 | Inspect the radiator cap. Is the radiator cap faulty? | Go to Step 4 | Go to Step 5 |
| 4 | Perform a radiator cap pressure test. Replace the cap if necessary. Is a loss of coolant still evident? | Go to Step 5 | System OK |
| 5 | Inspect the following components: The coolant reservoir The hose Is the coolant recovery reservoir or the hose leaking? | Go to Step 6 | Go to Step 7 |
| 6 | Replace the reservoir or the hose. Is a loss of coolant still evident? | Go to Step 7 | System OK |
| 7 | Inspect the following components: The radiator The heater hoses The connections Is any damage evident? | Go to Step 8 | Go to Step 9 |
| 8 | Repair or replace the components as necessary in order to correct the leak. Is a loss of coolant still evident? | Go to Step 9 | System OK |
| 9 | Inspect the water pump seal. Is the water pump seal leaking? | Go to Step 10 | Go to Step 11 |
| 10 | Replace the water pump. Is a loss of coolant still evident? | Go to Step 11 | System OK |
| 11 | Inspect the water pump sealing surface. Is the water pump O-Ring leaking? | Go to Step 12 | Go to Step 13 |
| 12 | Replace the O-Ring. Is a loss of coolant still evident? | System OK | |
| 13 | Inspect the cylinder block, cylinder head and gasket surface. Is the cylinder block, cylinder head or gasket leaking? | Go to Step 14 | System OK |
| 14 | Repair or replace the components as necessary in order to correct the leak. Is a loss of coolant still evident? | System OK |
Loss of Coolant
Engine Fails To Reach Normal Operating Temperature
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Inspect the thermostat for the following conditions: The thermostat remains open. An incorrect thermostat is installed. Does either of the above conditions exist? | Go to Step 2 | Go to Step 3 |
| 2 | Install a new thermostat of the correct type and heat range. Does the engine still fail to reach the normal operating temperature? | Go to Step 3 | System OK |
| 3 | Inspect the coolant level. Is the coolant level below the ADD mark? | Go to Step 4 | Go to Step 5 |
| 4 | Add coolant. Does the engine still fail to reach the normal operating temperature? | Go to Step 5 | System OK |
| 5 | Inspect the radiator for the following conditions: Plugging A faulty cap Does either of the above conditions exist? | Go to Step 6 | Go to Step 7 |
| 6 | Inspect the radiator or the cap. Replace the cap as necessary. Does the engine reach the normal operating temperature? | System OK | Go to Step 7 |
| 7 | Inspect the cylinder head. Is the cylinder head or block cracked or plugged? | Go to Step 8 | |
| 8 | Repair the cylinder head or block as necessary. Does the engine reach the normal operating temperature? | System OK |
Engine Fails To Reach Normal Operating Temperature
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.
Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body.
From the cylinder heads, the coolant flows to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine reaches normal operating temperature, or 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 coolant 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.
Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is 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.
Scheme 4
The thermostat is a coolant flow control component. Its purpose is to help regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element (4). The element connects to a valve (2) through a small piston (1). When the element is heated, it expands and exerts pressure against the 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 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. After the coolant temperature reaches the 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, 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.
The thermostat begins opening at 82°C (179°F). The thermostat fully opens at 95°C (203°F). The valve lift when the thermostat is fully open measures at least 8 mm (0.31 in).
Scheme 5
An air bleed valve (2) is provided in the top of the thermostat. The air bleed valve vents any gas or air that has entered the cooling system.
Radiator
The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a tube and fin downflow 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 right rear side of the lower 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.
Coolant Recovery System
The coolant recovery system consists of a plastic coolant recovery reservoir and overflow tube. The recovery reservoir provides an air space in the cooling system that allows the coolant to expand and contract. The surge tank provides a coolant fill point and a central air bleed location. 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.
During vehicle use, the coolant heats and expands. The increased coolant volume flows into the recovery reservoir. As the coolant circulates, any air is allowed to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.
Scheme 6
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 calibrated spring, which protects the radiator from excessive cooling system pressure. The vacuum valve is held against its seat by a light 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 System Indicators
The ECT gauge is controlled by the instrument panel cluster (IPC). The IPC receives a signal from the PCM, which the IPC interprets and converts to a gauge reading.
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. Missing, damaged or incorrectly installed air baffles or seals may cause the engine to overheat.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the lower 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.
Cooling Fan Control
The engine cooling fan system consists of an electric cooling fan, two fan relays and a fan resistor. The fan 1 relay controls power to the fan motor. The fan 2 relay controls the ground path of the fan motor. The gauge fuse supplies ignition voltage to the coils of both the fan 1, and the fan 2 relays. The RDI fuse supplies battery voltage to the switch side of the fan 1 relay. The PCM controls the ground for the coils of both relays. The PCM controls low and high speed fan operation by energizing and de-energizing the fan 2 relay which changes the ground path of the fan motor.
During low speed operation, which is when the A/C is operating and the engine coolant temperature (ECT) is below 83°C (181°F), the PCM supplies the ground path for the fan 1 relay through the cooling fan 1 relay control circuit. This energizes the relay, closes the fan 1 relay contacts, and supplies battery voltage from the RDI fuse through the cooling fan motor supply voltage circuit to the fan motor. The ground path for the fan motor is through the closed contacts of the de-energized fan 2 relay, through the fan resistor to G103. The result is a series circuit with the fan running at low speed.
During high speed operation, which is when the ECT reaches 93°C (199°F) or the A/C system pressure exceeds 1520 kPa (220 psi), the PCM supplies the ground path for the fan 1 relay through the cooling fan 1 relay control circuit. This energizes the relay, closes the fan 1 relay contacts, and supplies battery voltage from the RDI fuse through the cooling fan motor supply voltage circuit to the fan motor. The PCM also supplies the ground path for the fan 2 relay. This energizes the relay, switches the fan 2 relay contacts, and supplies a ground for the fan motor directly to G103. The result is a series circuit with the fan running at high speed.
The A/C refrigerant pressure switch is in parallel with the PCM controlled ground for the coil of the fan 2 relay. If the A/C system pressure exceeds 1520 kPa (220 psi), the pressure switch closes the ground circuit to the coil of the fan 2 relay, initiating high speed fan operation.
The PCM commands low speed fan operation when all of the following conditions occur
- The A/C system is operating.
- The A/C system pressure is below 1226 kPa (178 psi).
- The engine coolant temperature (ECT) is below 83°C (181°F).
The PCM commands high speed fan operation when either of the following conditions occur
- The ECT reaches 93°C (199°F).
- The A/C system pressure exceeds 1520 kPa (220 psi).