The engine cooling system uses a coolant solution of DEX-COOL™ and clean, drinkable water. This coolant solution carries excess heat away from the engine block and the air compressor, if equipped.
A belt driven water pump moves the coolant solution through the cooling system of the engine. The coolant solution moves through the cooling system in the following manner:
- Heated coolant flows though the radiator.
- The heat is transferred to the outside air when the coolant is in the radiator.
- The cooled fluid flows back to the engine block.
The coolant solution dissipates heat as it passes through the radiator. The engine cooling fan pulls outside air past the radiator fins and tubes. The radiator transfers the heat from the coolant solution to this outside air.
The cooling fan is belt driven from the engine crankshaft. A thermostatic fan clutch drives the cooling fan. The thermostatic fan clutch controls the amount of torque that is transmitted from the engine crankshaft to the fan blades.
The clutch allows more torque to engage on the fan when the following conditions exist:
| • | The engine operating temperature increases. |
| • | The driving speed is low. |
The fan turns more quickly as the torque is increased. As a result, the fan draws more air through the radiator.
The thermostatic fan clutch disengages when the following condition exist:
| • | The engine temperature decreases. |
| • | The driving speed is high. |
A fan shroud and rubber baffles direct the air flow through the radiator.
The shroud and the baffles are mounted on the radiator lower mounting panel. Another baffle is mounted to the under side of the hood. The baffle that is mounted to the under side of the hood forms a seal at the top of the radiator.
The shroud and the baffles prevent the air from recirculating around the radiator. Missing or misaligned baffles may cause engine overheating.
Thermostats regulate the operating temperature of the engine. The thermostats are located in the coolant outlet at the front of the engine. The thermostats open and allow coolant to flow through the radiator when the engine reaches a predetermined temperature. The thermostats also control the amount of coolant that flows through the engine.
A pressure cap on the radiator or the surge tank regulates the cooling system pressure. The operating pressure of the cooling system rises as the coolant temperature increases.
Operating the system under pressure raises the boiling point of the coolant. A raised boiling point results in the following conditions:
| • | The possibility of boiling is reduced. |
| Boiling may be caused by the following conditions: |
| • | High altitude |
| • | High engine coolant temperatures |
| • | Cavitation is prevented. |
The pressure cap limits the cooling system pressure.
The cap uses two built-in valves:
| • | A pressure relief valve |
| • | A vacuum valve |
The two valves are normally closed.
The pressure relief valve opens when the coolant pressure exceeds the spring tension of the pressure valve. The pressure relief valve takes the following actions when the pressure exceeds 62 kPa (9 psi):
| • | The pressure relief valve vents the excess air pressure on vehicles equipped with a surge tank. |
| • | The pressure relief valve vents the coolant into the coolant recovery system. |
The vacuum valve opens in order to relieve the vacuum that is created when the following conditions exist:
| • | The engine coolant temperature becomes cold enough. |
| • | The atmospheric pressure is greater than the spring tension of the vacuum valve. |
Opening the vacuum valve allows the following actions to occur:
| • | Air re-enters the system on vehicles equipped with a surge tank. |
| • | Coolant re-enters the system from the recovery reservoir. |
| • | The hoses and other components that are not internally supported are prevented from collapse. |
The coolant recovery reservoirs and the surge tanks perform the following functions:
| • | Compensate for coolant fluid expansion |
| • | Help prevent coolant loss |
The coolant recovery reservoir or the surge tank is located on the radiator mounting panel.
Coolant recovery reservoirs are used on gasoline engines. The coolant recovery reservoirs are not pressurized.
Surge tanks are used on diesel engines. Surge tanks allow an air space in the cooling system. the air space allows the coolant to expand and to contract. Surge tanks operate under the regulated pressure setting of the pressure cap.
