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.
Engine Coolant Temperature Indicator Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Connector End View Reference: Cooling System Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Start the engine. Does the engine coolant temperature (ECT) indicator illuminate? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | With the scan tool, observe the Engine Coolant Temperature parameter in the powertrain control module (PCM) data list. Does the scan tool indicate that the coolant temperature is within the temperature range shown on the temperature gage? | Go to Engine Overheating | Go to Step 4 |
| 4 | Replace the instrument panel cluster (IPC). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | Go to Step 5 | |
| 5 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Engine Coolant Temperature Indicator Always On
Engine Overheating
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| 1 | Inspect for a loss of system pressure and/or coolant. Is there a loss of system pressure and/or coolant? | Go to Step 2 | Go to Step 3 | |
| 2 | Inspect and repair any faulty hose connections or radiator cap. Fill the system to the proper level, then retest. Does the engine still overheat beyond the specified value? | 125°C (257°F) | Go to Step 3 | System OK |
| 3 | Inspect the coolant concentration for low temperature protection below the specified value. Is the proper low temperature protection present? | 37°C (-34°F) | Go to Step 5 | Go to Step 4 |
| 4 | Replace the coolant. Refer to Draining and Filling Cooling System (LL8) or Draining and Filling Cooling System (LM4) . 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 in Engine Mechanical - 4.2L. 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 (LL8) or Water Pump Replacement (LM4) . 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 (4.2L Engine) or Thermostat Replacement (5.3L Engine) . 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 losing 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 Trouble Code (DTC) List - Vehicle in Vehicle DTC Information. Is the action complete? | Go to Step 3 | |
| 3 | Inspect the coolant level. Is the coolant at the proper level? | Go to Step 5 | Go to Step 4 |
| 4 | Fill the cooling system to the proper level. Refer to Draining and Filling Cooling System (LL8) or Draining and Filling Cooling System (LM4) . Is the action complete? | Go to Step 5 | |
| 5 | If the engine is suspected to have a coolant leak into the cylinder, the coolant can hydraulically lock the cylinder. Does the engine crankshaft rotate? | Go to Step 6 | Go to Step 30 |
| 6 | Engine overheating can cause a loss of coolant. Is the engine overheating? | Go to Step 31 | 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 33 | 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 32 | Go to Step 10 |
| 10 | With the engine idling, inspect the coolant recovery system. Does the coolant recovery system 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: The auxiliary heater The coolant bypass The coolant reservoir The heater The radiator Are any of the hoses, clamps, or pipes leaking? | Go to Step 21 | Go to Step 12 |
| 12 | Visually inspect the following components: The block heater The coolant pressure cap The coolant reservoir The core plugs The cylinder head gaskets The engine block The intake manifold The radiator The thermostat The water pump Are any of the listed components leaking? | Go to Step 21 | 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 21 | 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 22 |
| 15 | Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure? | Go to Step 34 | Go to Step 22 |
| 16 | Inspect for the following conditions: A coolant smell inside of the vehicle Coolant in the HVAC module drain tube Coolant on the vehicles floor covering under the HVAC module Is coolant present? | Go to Step 23 | Go to Step 17 |
| 17 | If equipped with auxiliary heating, inspect for the following: A coolant smell inside of the vehicle Coolant in the auxiliary HVAC module drain tube Coolant on the floor covering near the auxiliary HVAC module Is coolant present? | Go to Step 24 | Go to Step 18 |
| 18 | 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 19 | Go to Step 20 |
| 19 | Inspect the engine oil fluid level indicator for a gray/white milky substance. Is there a milky substance on the engine fluid level indicator? | Go to Step 25 | Go to Step 20 |
| 20 | 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 27 | Go to Step 35 |
| 21 | Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete? | Go to Step 35 | |
| 22 | Replace the coolant pressure cap. Is the repair complete? | Go to Step 35 | |
| 23 | Replace the heater core. Refer to Heater Core Replacement in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 35 | |
| 24 | Replace the auxiliary heater core. Refer to Heater Core Replacement - Auxiliary in Heating, Ventilation and Air Conditioning. Is the repair complete? | Go to Step 35 | |
| 25 | Remove the engine oil cooler lines from the radiator, if equipped. Pressure test the cooling system. Refer to Cooling System Leak Testing . Inspect the engine oil cooler for coolant. Is coolant present in the engine oil cooler? | Go to Step 26 | Go to Step 29 |
| 26 | Replace the radiator. Refer to Radiator Replacement (LL8) or Radiator Replacement (LM4) . Service the engine oil and filter. Refer to Engine Oil and Oil Filter Replacement in Engine Mechanical - 4.2L or Engine Oil and Oil Filter Replacement in Engine Mechanical - 5.3L. Is the repair complete? | Go to Step 35 | |
| 27 | 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 in the transmission oil cooler? | Go to Step 28 | Go to Step 29 |
| 28 | Replace the radiator. Refer to Radiator Replacement (LL8) or Radiator Replacement (LM4) . Service the automatic transmission. Refer to Automatic Transmission Fluid/Filter Replacement in Automatic Transmission - 4L60-E/4L65-E. Is the repair complete? | Go to Step 35 | |
| 29 | Install the cooler lines to the radiator. Is the repair complete? | Go to Step 35 | |
| 30 | Repair the engine no crank condition. Refer to Engine Will Not Crank - Crankshaft Will Not Rotate in Engine Mechanical - 4.2L or Engine Will Not Crank - Crankshaft Will Not Rotate in Engine Mechanical - 5.3L. Is the repair complete? | Go to Step 35 | |
| 31 | Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete? | Go to Step 35 | |
| 32 | Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber in Engine Mechanical - 4.2L or Coolant in Engine Oil in Engine Mechanical - 5.3L. Is the repair complete? | Go to Step 35 | |
| 33 | Repair the engine knock. Refer to Lower Engine Noise, Regardless of Engine Speed in Engine Mechanical - 4.2L or Lower Engine Noise, Regardless of Engine Speed in Engine Mechanical - 5.3L. Is the repair complete? | Go to Step 35 | |
| 34 | Repair the combustion pressure in the cooling system problem. Refer to Cylinder Leakage Test in Engine Mechanical - 4.2L or Cylinder Leakage Test in Engine Mechanical - 5.3L. Is the repair complete? | Go to Step 35 | |
| 35 | 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 (LL8) or Coolant Heater Replacement (LM4) . 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 (LL8) or Draining and Filling Cooling System (LM4) . 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 (4.2L Engine) or Thermostat Replacement (5.3L Engine) . 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 38185 Hose Clamp Pliers
- J 26568 Coolant and Battery Fluid Tester. See «Special Tools»(ref-200409-S17093269022005102000000) .
Coolant Filling Procedure
- If a complete block drain was required, install the plug.
- Install the lower radiator hose.
- Using J 38185 slide the clamp into the original position.
- Lower the vehicle.
- Remove coolant recovery reservoir cap.
- Fill the coolant recovery reservoir with the remaining coolant.
- Install coolant recovery reservoir cap.
- Install the radiator 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 recovery reservoir as necessary.
- Rinse away any excess coolant from the engine and the engine compartment.
- Inspect the cooling system for leaks.
- Inspect the concentration of the engine coolant using J 26568 . See «Special Tools»(ref-200409-S17093269022005102000000) .
Note. The procedure below must be followed. Improper coolant level could result in a low or high coolant level condition, causing engine damage.
- If a complete block drain was required, install the coolant heater or plug. Refer to «Coolant Heater Replacement (LL8)»(ref-200409-S15674786282005102000000) or «Coolant Heater Replacement (LM4)»(ref-200409-S16010780652005102000000) .
- Install the lower radiator hose.
- Using the J 38185 slide the clamp into the original position.
- Lower the vehicle.
- Install the radiator cap.
- Remove coolant recovery reservoir cap.
- Slowly add a mixture of 50/50 DEX-COOL antifreeze and deionized water to the cooling system through the coolant recovery reservoir. Refer to «Capacities - Approximate Fluid»(ref-200403-S02268484942005102000000) in General Information.
- Fill the coolant recovery reservoir with the remaining coolant.
- Install coolant recovery reservoir cap.
- Install the coolant air bleed hose to the throttle body.
- Using J 38185 slide the coolant air bleed hose clamp back to the original position.
- Start the engine.
- Run the engine from 1,000-3,000 RPM in 30-second intervals until the engine reaches normal operating temperature.
- Allow the engine to idle for 3 minutes before repeating the last step.
- Shut the engine OFF.
- Allow the engine to cool.
- Top off the coolant recovery reservoir as necessary.
- Rinse away any excess coolant from the engine and the engine compartment.
- Inspect the cooling system for leaks.
- Inspect the concentration of the engine coolant using J 26568 . See «Special Tools»(ref-200409-S17093269022005102000000) .
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 46406 Fan Clutch Remover and Installer. See Special Tools .
J 43244 Relay Puller Pliers
J 38185 Hose Clamp Pliers
Tool Required
J 41240 Fan Clutch Remover and Installer
J 38185 Hose Clamp Pliers
J 38185 Hose Clamp Pliers
Cooling Fan Control
The purpose of the electro-viscous (EV) fan clutch is to maintain powertrain cooling requirements. The powertrain control module (PCM) monitors the following sensors to regulate the fan speed
- Engine coolant temperature sensor
- A/C refrigerant pressure sensor
- Vehicle speed sensor
- Intake air temperature sensor
- Transmission fluid temperature sensor
- Ambient air temperature sensor
The PCM controls the electro-viscous fan clutch engagement. The PCM regulates a 12-volt pulse width modulated signal (PWM) to the cooling fan relay. The PWM signal determines the ON time of the relay. As the commanded state of the fan clutch increases, so does the ON time of the relay. This ON time directly effects the amount of time the solenoid, which is internal to the fan clutch, is energized. When the solenoid in the fan clutch is energized, it opens the spring loaded valve and allows fluid to flow from the storage chamber to the fluid coupling of the cooling fan clutch, increasing the fan speed. When the solenoid is de-energized, the spring loaded valve closes, and blocks the path of the fluid to the fluid coupling of the fan clutch, reducing fan speed.
The fan has the ability to create a feedback signal, so the PCM has an actual fan speed input. This is done with a hall effect sensor internal to the fan clutch. The PCM supplies a 5-volt reference and a low reference to the hall effect sensor. The hall effect sensor returns a signal pulse through the cooling fan speed signal circuit in response to the reluctor track passing by the magnetic field of the hall effect sensor.
The PCM commands the cooling fan to 100% under the following conditions
- Engine coolant temperature exceeds approximately 129°C (264°F).
- The transmission oil temperature exceeds approximately 151°C (304°F).
- A/C refrigerant pressure exceeds 1655 kPa (240 psi).
- When certain DTC's set. These include P0116, P0117, P0118, P0125, P1481, P1482, and P1484.
The scan tool can engage the cooling fan clutch. This is done with the engine controls special function menu screen. To engage the cooling fan, It can take up to 2 minutes for a 100% command with the engine at 2000 RPM. The lower the engine speed, the longer it will take the fan to engage. To disengage the cooling fan, it can take up to 2 minutes with the engine at 2000 RPM. The lower the engine speed, the longer it will take to disengage. In lower ambient air temperatures the cooling fan will engage in less time, however, it will take longer to disengage due to the properties of the fluid vs. temperature.
Under certain conditions the cooling fan may be engaged at engine restart. They are as follows
- The cooling fan was engaged at the time the engine was turned off
- The fluid may bleed from the storage chamber into the fluid coupling of the cooling fan
Although the fan is commanded off at this time due to a cold start condition. This is the most likely time a vehicle driver will notice that the fan noise is excessive compared to normal engine starts with out cooling fan engaged. As the engine speed is increased the fan noise will be louder than before. These are normal conditions that can be very intermittent.
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 performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.
The IPC turns OFF the engine coolant indicator when the engine coolant falls below 122°C (252°F).
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately 1/3 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 jackets surrounding the cylinders, where the coolant 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 the coolant absorbs 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 thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or the coolant will flow through the thermostat and into the radiator where the coolant is cooled and the coolant cycle is completed.
Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components, which are described below
- The coolant
- The radiator
- The pressure cap
- The coolant recovery system
- The air baffles and seals
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, consisting of a core and 2 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 left hand tank. The drain cock unit includes the drain cock and drain cock seal.
The radiator removes heat from the coolant passing through the core. The fins on the core transfer heat from the coolant passing through the tubes. As air passes between the fins, the air removes the heat and cools the coolant.
Pressure Cap
The pressure cap seals the cooling system, and contains a blow-off or pressure valve, and a vacuum or atmospheric valve. The pressure valve is held against the seat by a spring, which protects the radiator from excess cooling system pressure. The vacuum valve is held against the seat by a spring, which permits the opening of the valve to relieve the vacuum created in the cooling system as the coolant 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, the pressure valve opens, 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 Recovery System
The coolant recovery system consists of a plastic coolant recovery reservoir and overflow tube. The recovery reservoir is also called a recovery tank or expansion tank. This reservoir 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, the pressure valve opens in the pressure cap. This allows the coolant, which has expanded due to being heated, is allowed 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, coolant is not lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. An advantage to using a coolant recovery reservoir is that most of the air bubbles are eliminated from the cooling system. 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 cooling system capability. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle and through the radiator to increase engine cooling. Air baffles are also used to direct airflow through the radiator and increase cooling capability. Air seals prevent air from bypassing the radiator and A/C condenser, and prevent recirculation of hot air for better hot weather cooling and A/C condenser performance.
Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is mounted on the pump shaft and consists of a series of flat or curved blades or vanes on a flat plate. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force.
The impeller shaft is supported by one or more sealed bearings. The sealed bearings never need to be lubricated. Grease cannot leak out, dirt and water cannot get in as long as the seal is not damaged or worn.
The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.
Thermostat
The thermostat is a coolant flow control component. Its purpose is to help regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a small piston. When the element is heated, it expands and exerts pressure against 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.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant in the radiator.
The transmission oil pump, pumps the fluid through the transmission oil cooler line to the transmission oil cooler. The fluid then flows through the cooler where the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.
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.