Engine Cooling, Basic Function - GF20.00-P-1002A

Engine All (4xWD) 

Engine All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 

General 

The engine cooling has the following tasks:

• Establishing or maintaining thermal balance, depending on the engine operating point
• Quickly establishing the engine operating temperature
• Heating the vehicle interior
• Releasing excess waste heat into the environment
• Lubricating the circulation pumps through additives in the coolant

Function requirements 

• Engine management ON (circuit 87M)
• Engine in operation

Function 

Air/water recirculation cooling is a combined system of liquid and air cooling. The waste heat is released into the environment through the coolant via the radiator.

The coolant essentially absorbs the waste heat of the following components:

• Cylinder head
• Crankcase
• Turbocharger
• Exhaust gas recirculation
• Dual clutch transmission
• Automatic transmission

The coolant essentially absorbs the waste heat of the following media:

• Engine oil
• Gear oil
• Charge air

Part of the heat released by the combustion engine is used for heating the vehicle interior.

The engine oil can be heated or cooled with the released heat. This is implemented via the engine oil heat exchanger.

The circulation pump delivers the coolant through the cooling circuits. A distinction is made between the following types of circulation pumps:

• Mechanically driven circulation pumps
• Electrical circulation pumps

The coolant temperature is measured by the coolant temperature sensor and constitutes the calculation basis for the engine cooling system control and the composition of the fuel/air mixture. A near-engine mounted coolant temperature sensor measures the actual coolant temperature value and permanently transmits it to the combustion engine control unit.

The coolant thermostat is the shift element between the near-engine mounted cooling circuit and the cooling circuit with the radiator. The coolant thermostat can adopt different positions depending on the coolant temperature. The basic positions of the coolant thermostat are:

• Full throttling position: The coolant flows through the near-engine mounted cooling circuit.
• Mixed-fuel mode position: The coolant partially flows through the radiator.
• Radiator operation position: The coolant flows through the near-engine mounted cooling circuit and the radiator.

Depending on the version, the coolant thermostat can adopt multiple positions.

Air ducts and shutters installed in the body take in the fresh air and distribute it to the components to be cooled.

The fan supports the flow of ambient air through the radiator, e.g. at high outside temperatures. The fan is electrically driven.

The following components are cooled by fresh air in addition:

• Radiator
• Charge air cooler
• Heat exchanger, e.g. transmission oil heat exchanger or engine oil heat exchanger

The powertrain control unit controls the radiator shutters, radiator trim flaps and charge air cooling.

To protect the engine from corrosion and freezing, an additive consisting of antifreeze and anti-corrosion agent is added to the cooling medium.

	Additional basic functions
	Coolant circuit, basic function		GF20.00-P-1003A
	Cooling-air flow, basic function		GF20.40-P-1000A
	Combustion engine control unit, basic function		GF07.08-P-9890A
	Powertrain control unit, basic function		GF54.21-P-9894A
	Coolant temperature sensor, basic function		GF07.04-P-2002A
	Coolant thermostat, basic function		GF20.10-P-1001A
	Coolant circulation pump, basic function		GF20.10-P-2002A
	Coolant pump, basic function		GF20.10-P-2005A