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
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The engine cooling fan motor runs continuously in high or low speed. | |||
| 1 | Did you perform the Engine Cooling Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Engine Cooling |
| 2 | Turn ON the ignition, with the engine OFF. Is the engine cooling fan ON? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Disconnect the cooling fan 1 relay. Is the engine cooling fan ON? | Go to Step 4 | Go to Step 8 |
| 4 | Disconnect the cooling fan 2 relay. Is the engine cooling fan ON? | Go to Step 5 | Go to Step 9 |
| 5 | Turn OFF the ignition. Disconnect the cooling fan connector. Turn ON the ignition, with the engine OFF. Probe the low speed cooling fan supply voltage circuit of the cooling fan 1 relay with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 6 | Go to Step 7 |
| 6 | Repair the short to voltage in the low speed cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | |
| 7 | Repair the short to voltage in the high speed cooling fan motor supply voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 12 | |
| 8 | Inspect for poor connections at the cooling fan 1 relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs. Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
| 9 | Inspect for poor connections at the cooling fan 2 relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Repairs. Did you find and correct the condition? | Go to Step 12 | Go to Step 11 |
| 10 | Replace the cooling fan 1 relay. Refer to Cooling Fan Relay Replacement (Low Speed) or Cooling Fan Relay Replacement (High Speed) . Did you complete the replacement? | Go to Step 12 | |
| 11 | Replace the cooling fan 2 relay. Refer to Cooling Fan Relay Replacement (Low Speed) or Cooling Fan Relay Replacement (High Speed) . 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: The engine cooling fan motor is inoperative in either high, low, or both speeds. | |||
| 1 | Did you perform the Engine Cooling Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Engine Cooling |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the Low Speed Fan Relay ON and OFF. Does the cooling fan turn ON and OFF with each command? | Go to Step 3 | Go to Step 4 |
| 3 | With a scan tool, command the high speed fan relay ON and OFF. Does the cooling fan turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 7 |
| 4 | Disconnect the cooling fan 1 relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the cooling fan 1 relay with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 |
| 5 | Connect the cooling fan 1 relay. Disconnect the cooling fan. Probe the low speed cooling fan supply voltage circuit with a test lamp connected to a good ground. With a scan tool, command the Low Speed Fan Relay ON and OFF. Does the test lamp turn ON and OFF with each command? | Go to Step 6 | Go to Step 9 |
| 6 | Probe the ground circuit of the cooling fan with a test lamp connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 13 | Go to Step 12 |
| 7 | Disconnect the cooling fan 2 relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the cooling fan 2 relay with a test lamp connected to a good ground. Does the test lamp illuminate? | Go to Step 8 | Go to Step 11 |
| 8 | Connect the cooling fan 2 relay. Disconnect the cooling fan. Probe the high speed cooling fan supply voltage circuit with a test lamp connected to a good ground. With a scan tool, command the High Speed Fan Relay ON and OFF. Does the test lamp turn ON and OFF with each command? | Go to Step 13 | Go to Step 10 |
| 9 | Test the low speed cooling fan supply voltage circuit for a high resistance and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 15 |
| 10 | Test the high speed cooling fan supply voltage circuit for a high resistance and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 16 |
| 11 | Repair the battery positive voltage circuit of the cooling fans. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 12 | Repair the ground circuit of the cooling fan. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 21 | |
| 13 | Inspect for poor connections at the harness connector of the cooling fan. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 21 | Go to Step 17 |
| 14 | Inspect for poor connections 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 21 | Go to Step 18 |
| 15 | Inspect for poor connections at the harness connector of the cool 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 21 | Go to Step 19 |
| 16 | Inspect for poor connections at the harness connector of the cool 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 21 | Go to Step 20 |
| 17 | Replace the cooling fan. Refer to Cooling Fan Replacement - Electric . Did you complete the replacement? | Go to Step 21 | |
| 18 | IMPORTANT: Program the PCM. Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L. | Go to Step 21 | |
| 19 | Replace the cool fan 1 relay. Refer to Cooling Fan Relay Replacement (Low Speed) or Cooling Fan Relay Replacement (High Speed) . Did you complete the replacement? | Go to Step 21 | |
| 20 | Replace the cool fan 2 relay. Refer to Cooling Fan Relay Replacement (Low Speed) or Cooling Fan Relay Replacement (High Speed) . Did you complete the replacement? | Go to Step 21 | |
| 21 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| IMPORTANT |
|---|
| Program the PCM. |
Cooling Fan Inoperative
Engine Overheating
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Inspect for a loss of system pressure. Is there a loss of system pressure? | Go to Step 2 | Go to Step 3 | |
| 2 | Inspect and repair any faulty hose connections or radiator cap. Does the engine still overheat beyond the specified value? | 37° F (-34° F) | Go to Step 3 | System OK |
| 3 | Inspect the coolant temperature for low temperature below the specified value. Is low temperature protection present? | 37° F (-34° F) | Go to Step 5 | Go to Step 4 |
| 4 | Replace the coolant. Refer to Draining and Filling Cooling System . Does the engine still overheat? | Go to Step 5 | System OK | |
| 5 | Inspect the drive belt for excessive wear or low tension. Is the drive belt worn or is the tension too low? | Go to Step 6 | Go to Step 7 | |
| 6 | Replace the drive belt. Refer to Drive Belt Replacement - Accessory . Does the engine still overheat? | Go to Step 7 | System OK | |
| 7 | Inspect the radiator fins for obstruction. Are the radiator fins obstructed? | Go to Step 8 | Go to Step 9 | |
| 8 | Inspect and clean the radiator. Refer to Radiator Cleaning . Does the engine still overheat? | Go to Step 9 | System OK | |
| 9 | Inspect the water pump for physical damage. Is the water pump damaged or inoperative? | Go to Step 10 | Go to Step 11 | |
| 10 | Replace the water pump. Refer to Water Pump Replacement . Does the engine still overheat? | Go to Step 11 | System OK | |
| 11 | Inspect the cooling system passages for obstruction. Is the cooling system passage blocked? | Go to Step 12 | Go to Step 13 | |
| 12 | Inspect and flush the system. Refer to Flushing . Does the engine still overheat? | Go to Step 13 | System OK | |
| 13 | Inspect the electro-viscous fan. Is the electro-viscous fan inoperative? | Go to Step 14 | Go to Step 15 | |
| 14 | Replace the electro-viscous fan. Does the engine still overheat? | Go to Step 15 | System OK | |
| 15 | Inspect for a stuck thermostat. Refer to Thermostat Diagnosis . Is the thermostat stuck in the closed position? | Go to Step 16 | Go to Step 17 | |
| 16 | Replace the thermostat. Refer to Thermostat Replacement . Does the engine still overheat? | Go to Step 17 | System OK | |
| 17 | The following factors may cause the engine to overheat: A heavy vehicle payload The A/C system Excess engine oil Restricted air flow through the radiator Extreme air temperature Correct or repair as necessary. Does the engine still overheat? | System OK |
Engine Overheating
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 System Check - 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 engine. Does the engine crankshaft rotate? | Go to Step 6 | Go to Step 26 |
| 6 | Engine overheating can cause a loss of coolant. Is the engine overheating? | Go to Step 27 | Go to Step 7 |
| 7 | Extended operation with a low coolant level can cause engine internal component failure. Is the engine knocking? | Go to Step 29 | 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 28 | Go to Step 10 |
| 10 | With the engine idling, inspect the coolant surge tank. Does the coolant surge tank discharge coolant while the engine is idling? | Go to Step 15 | Go to Step 11 |
| 11 | Visually inspect the hoses, pipes and hose clamps at the following locations: Coolant surge tank Heater core Radiator Are any of the hoses, clamps or pipes leaking? | Go to Step 20 | Go to Step 12 |
| 12 | Visually inspect the following components: Coolant pressure cap Core plugs Cylinder head gaskets Engine block Intake manifold Radiator Thermostat housing Water pump Are any of the listed components leaking? | Go to Step 20 | Go to Step 13 |
| 13 | Pressure test the cooling system. Refer to Cooling System Leak Testing . With the cooling system pressurized, visually inspect the components listed in steps 11 and 12. Are any leaks present? | Go to Step 20 | 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 21 |
| 15 | Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure? | Go to Step 30 | Go to Step 21 |
| 16 | Inspect for the following conditions: A coolant smell inside of the vehicle Coolant in the HVAC module drain tube Coolant on the vehicle floor covering near the HVAC module Is coolant present? | Go to Step 22 | Go to Step 17 |
| 17 | Inspect the underside of the engine 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 19 |
| 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 28 | Go to Step 19 |
| 19 | Inspect the automatic transmission oil fluid level indicator, if equipped, for a gray/white milky substance. Is there a milky substance on the automatic transmission fluid level indicator? | Go to Step 23 | Go to Step 31 |
| 20 | Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete? | Go to Step 31 | |
| 21 | Replace the coolant pressure cap. Is the repair complete? | Go to Step 31 | |
| 22 | Replace the heater core. Refer to Heater Core Replacement in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 31 | |
| 23 | Remove the transmission oil cooler lines from the radiator. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the transmission oil cooler for coolant. Is coolant present? | Go to Step 24 | Go to Step 25 |
| 24 | Replace the radiator. Refer to Radiator Replacement . Service the automatic transmission. Refer to Engine Coolant/Water in Transmission in Automatic Transmission - 4L60-E/4L65-E. Is the repair complete? | Go to Step 31 | |
| 25 | Install the cooler lines to the radiator. Refer to Transmission Fluid Cooler Hose/Pipe Replacement in Automatic Transmission - 4L60-E/4L65-E. Is the action complete? | Go to Step 31 | |
| 26 | Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate in Engine Mechanical - 4.8L, 5.3L, and 6.0L. Is the repair complete? | Go to Step 31 | |
| 27 | Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete? | Go to Step 31 | |
| 28 | Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber or to Coolant in Engine Oil in Engine Mechanical - 4.8L, 5.3L, and 6.0L. Is the repair complete? | Go to Step 31 | |
| 29 | Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed in Engine Mechanical - 4.8L, 5.3L, and 6.0L. Is the repair complete? | Go to Step 31 | |
| 30 | Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test in Engine Mechanical - 4.8L, 5.3L, and 6.0L. Is the repair complete? | Go to Step 31 | |
| 31 | 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
Coolant Heater Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| Connector End View Reference: Cooling System Connector End Views | |||
| 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 . Did you complete the repair? | 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 . Did you complete the repair? | 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
Engine Fails To Reach Normal Operating Temperature
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you review the Symptoms - Engine Cooling Diagnosis information and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Verify that the engine does not reach normal operating temperature. Does the engine reach normal operating temperature? | System OK | Go to Step 3 |
| 3 | Inspect the coolant level. Is the coolant level below the add mark? | Go to Step 4 | Go to Step 5 |
| 4 | Add coolant as necessary. Refer to Draining and Filling Cooling System . Perform a cooling system pressure test. Is the repair complete? | System OK | Go to Step 5 |
| 5 | Inspect for a stuck open, missing, or wrong type of thermostat. Refer to Thermostat Diagnosis . Is the thermostat operating properly? | System OK | Go to Step 6 |
| 6 | Install the correct replacement thermostat. Refer to Thermostat Replacement . Is the repair complete? | System OK | Go to Step 7 |
| 7 | Run the engine in order to verify the repair. Does the engine fail to reach normal operating temperature? | Go to Step 1 | System OK |
Engine Fails To Reach Normal Operating Temperature
Tools Required
J 26568 Coolant and Battery Fluid Tester. See Special Tools and Equipment .
Filling Procedure
- Raise and support the vehicle.
- Lubricate the drain cock O-ring with clean coolant prior to installation.
- Install the radiator drain cock. Tighten: Tighten the radiator drain cock to 2 N.m (18 lb in).
- Lower the vehicle.
- Slowly fill the cooling system with a 50/50 coolant mixture. Refer to «Capacities - Approximate Fluid»(ref-187835-S41718988712005090100000) in Maintenance and Lubrication.
- Install the coolant pressure 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.
- Top off the coolant as necessary.
- Inspect the concentration of the engine coolant. Using the J 26568 . See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .
- Rinse away any excess coolant from the engine and the engine compartment.
- Inspect the cooling system for leaks.
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. See Special Tools and Equipment .
J 38185 Hose Clamp Pliers. See Special Tools and Equipment .
J 38185 Hose Clamp Pliers. See Special Tools and Equipment .
J 38185 Hose Clamp Pliers. See Special Tools and Equipment .
Cooling Fan Control
The engine cooling fan system consists of an electrical cooling fan and two fan relays. The relays provides 2 separate voltage supply circuits to the electric cooling fan. The ground path is provided at G105. The cooling fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. They are controlled by the powertrain control module (PCM).
During low speed operation, the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the low speed cooling fan supply voltage circuit to the electric cooling fan. There is an inline resistor internal to the cooling fan that creates a lower voltage for the cooling fan to obtain low speed operation.
During high speed operation the PCM supplies the ground path for the cooling fan 2 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides battery positive voltage for the cooling fan through the high speed cooling fan supply voltage circuit.
The low speed cooling fan is commanded ON when the coolant temperature reaches 108° C (226° F). It is turned OFF if the coolant temperature lowers to 104° C (219° F). The high speed cooling fan is commanded ON when the coolant temperature reaches 113° C (235° F). It is turned OFF if the coolant temperature lowers to 108° C (226° F). When the A/C is ON and the coolant temperature reaches 85° C (185° F), the low speed cooling fan will be turned ON at vehicle speeds less than 56 km/h (35 mph).
If engine temperatures are to low for cooling fan operation the PCM will command the cooling fans to cool the A/C condenser. The low speed cooling fan will commanded on at 1379 kPa (200 psi). Then commanded off at 1034 kPa (150 psi). The high speed cooling fan will be commanded on at 1586 kPa (230 psi). Then commanded off at 1482 kPa (215 psi).
ENGINE COOLANT HOT IDLE ENGINE
The radio activates an audible warning as requested by the instrument panel cluster (IPC). The IPC sends a class 2 message to the radio indicating the chime duration of 4 pulses. The warning sounds and the appropriate indicator illuminates in the driver information center (DIC) when the following occurs
- The IPC determines that the coolant temperature is greater than 125° C (257° F). The IPC receives a class 2 message from the PCM indicating coolant temperature.
- The IPC turns OFF the message when the engine coolant temperature falls below 122° C (252° F).
ENGINE OVERHEATED STOP ENGINE
The radio activates an audible warning as requested by the instrument panel cluster (IPC). The IPC sends a class 2 message to the radio indicating the chime duration of 4 pulses. The warning sounds and the appropriate indicator illuminates in the driver information center (DIC) when the following occurs
- The IPC determines that the coolant temperature is greater than 127° C (261° F). The IPC receives a class 2 message from the PCM indicating coolant temperature.
- The IPC turns OFF the message when the engine coolant falls temperature below 125° C (257° F). Then displays the ENGINE COOLANT HOT IDLE ENGINE message.
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.
Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Coolant will then be pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through 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.
Some coolant is also pumped from the water pump to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.
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, 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. During normal operating temperatures, the coolant assists in regulating the throttle body temperature.
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 two tanks. The aluminum core is a tube and fin crossflow design that extends from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer to the atmosphere.
The inlet and outlet tanks are a molded, high temperature, nylon reinforced plastic material. A high temperature rubber gasket seals the tank flange edge to the aluminum core. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core.
The radiator also has a drain cock located in the bottom of the right hand tank. In the radiator mount, 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.
Surge Tank
The surge tank is a plastic tank with a threaded 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 that allows the coolant to expand and contract. The surge tank provides a coolant fill point and a central air bleed location.
During vehicle use, the coolant heats 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.
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.
Coolant Heater
The optional engine coolant heater (RPO K05) is rated at 400 watts and supplies 1365 btu/hr. The engine coolant heater 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.