Description And Operation
The engine cooling system is divided into two independent sub-systems:
- A High Temperature (HT) cooling system that controls the temperature of the engine coolant.
- A Low Temperature (LT) cooling system that controls the coolant temperature of the intercooler.
Main components of the high temperature cooling system:
P. Engine coolant pump driven by the engine accessory drive belt
T. Coolant temperature control valve (Electronically actuated thermostat)
R. Engine cooling system radiator
Functional diagram of the high temperature cooling system:
P. Engine coolant pump driven by the engine accessory drive belt
T. Coolant temperature control valve (Electronically actuated thermostat)
R. Engine cooling system radiator
A. Passenger compartment heater core
C. Low pressure EGR heat exchanger
Main components of the low temperature cooling system:
P. Turbocharger air cooling system coolant pump controlled by the Powertrain Control Module (PCM)
T. Charge air cooler temperature control solenoid valve
R. Intercooler cooling system radiator
Functional diagram of the low temperature cooling system:
P. Turbocharger air cooling system coolant pump controlled by the Powertrain Control Module (PCM)
T. Charge air cooler temperature control solenoid valve
R. Intercooler cooling system radiator
The high temperature (HT) cooling circuit cools the following systems:
- Engine block
- Cylinder head
- Engine oil in the oil cooler
- Exhaust gas in the low pressure EGR heat exchanger
The coolant is cooled by a center mounted main radiator, behind the front bumper. The main radiator uses the dynamic air flow produced by the vehicle's speed and the forced air flow from the electric fan
The engine coolant is also routed to the heater core to heat the passenger compartment.
The high temperature cooling system is kept at a pressure of 1.4 bar.
The major components of the high temperature cooling system are:
- Pressurized coolant bottle
- Radiator
- Coolant temperature control valve (Electronically actuated thermostat)
- Coolant pump
- Passenger compartment heater core connection
- Low pressure EGR heat exchanger
- Engine oil heat exchanger (oil cooler)
The Coolant temperature control valve (5) functions as the engine thermostat and is electrically controlled by the PCM. It has one inlet from the engine cylinder head (1), an outlet to the radiator (4) to coolant pump inlet (2) and an outlet to the radiator inlet (3).
Coolant temperature control valve features:
A. Coolant inlet from the engine cylinder head
B. Coolant outlet to the coolant pump inlet tube
C. Coolant outlet to the radiator
1. Electric actuator
2. Flow diverter valve
The electric actuator (1) moves the flow diverter valve (2) through a dedicated shaft which diverts the flow from the radiator inlet to the coolant pump inlet.
When the diverter valve is in position (1), the thermostat is open. The flow from the engine is sent to the radiator inlet.
When the diverter valve is in position (2), the thermostat is closed. The flow from the engine is sent to the coolant pump inlet.
The major features of the centrifugal coolant pump:
- Pump pulley
- Coolant inlet tube
- Pump outlet to engine block
- Connection to the heat exchanger for cooling the EGR exhaust gas
- Connection to the heat exchanger for cooling the engine oil (oil cooler)
- Connection to the passenger compartment heater core
Coolant enters the engine at the engine block (1) and exits the engine at the cylinder head (2).
The high temperature pressurized coolant bottle (1) has a bottom outlet pipe (2) to the coolant pump inlet and a degassing pipe (3) to the cylinder head.
When the coolant temperature control valve (1) is closed, the coolant passes from inlet A (from the engine) to outlet B, and then goes to the pump inlet (2).
When the coolant temperature control valve (1) is open, the coolant passes from inlet A (from the engine) to outlet C, and then goes to the radiator inlet.
The engine oil cooler (1) is located on the exhaust-side of the engine block and receives coolant from an internal cavity (2) within the engine block.
The oil cooler receives coolant from an internal passage (A) within the engine block.
Coolant enters the oil cooler from the engine block (2) and exits the oil cooler through a hose (1) connected to the coolant pump inlet tube.
Coolant enters the low pressure EGR cooler (1) from the engine block (2) and exits the cooler through a hose (3) connected to the coolant pump inlet tube.
The coolant enters the passenger compartment heater core through the pipe (1) connected to the pipe that takes the coolant flow from the cylinder head to the coolant temperature control valve.
The coolant exits the passenger compartment heater core through the pipe (2) connected to the coolant pump inlet tube.
The major components of the low temperature cooling system are:
- Charge air cooler temperature control solenoid valve
- Turbocharger air cooling system coolant pump
- Pressurized coolant bottle
- Radiator
- Intercooler
- Turbocharger
The charge air cooler temperature control solenoid valve is electrically controlled by the PCM. The valve has an inlet (Z) from the intercooler, an outlet (A) to the coolant pump and an outlet (B) to the radiator inlet.
The turbocharger air cooling system coolant pump has a coolant inlet (1) and a coolant outlet (2).
The low temperature pressurized coolant bottle has a bottom outlet pipe (3) to the turbocharger (2) and a degassing pipe (1) to the radiator.
The intercooler (2) is mounted in the intake manifold (1).
The coolant outlet flow from the electric pump P, enters the intercooler inlet (3). From the intercooler outlet (4), the flow goes to the temperature control valve inlet Z. When the PCM activates the valve, it sends the flow to the outlet A from which it returns to the inlet of the electric pump P.
When the PCM deactivates the valve, it sends the flow to the outlet B from which it is directed to the radiator inlet. From the radiator outlet, the coolant goes to the inlet of the electric pump P.