Coolant Circuit, Basic Function - GF20.00-P-1003A

Engine All (4xWD) 

Engine All (CAR) 

Courtesy of MERCEDES-BENZ USA

Sample schematic diagram of coolant circuits 

Overview 

This document contains information on:

• General 
• Function 

General 

The engine cooling system comprises multiple cooling circuits depending on the components. The cooling circuits are closed systems which use coolant to transfer heat to the surroundings.

Function 

The engine cooling system is generally made up of the following cooling circuits:

• Engine cooling circuit
• Low-temperature circuits
• Heating circuit

The engine cooling circuit generally consists of the following components:

• Radiator
• Coolant expansion reservoir
• Engines coolant circuit coolant pump
• Coolant temperature sensor
• Coolant thermostat
• Crankcase and cylinder head
• Engine oil heat exchanger

Depending on the drivetrain and equipment, further components, such as an exhaust gas turbocharger or exhaust gas recirculation cooler, may also be integrated in the engine cooling circuit.

The low-temperature circuits may include the following components:

• Low-pressure cooler
• Coolant circulation pump
• Transmission oil heat exchanger
• Charge air cooler
• Switchover valve
• Coolant temperature sensor
• Electric machine
• Power electronics
• 48 V battery module
• High-voltage battery

The cooling of the 48 V battery module and/or the high-voltage battery takes place in its own separate low-temperature circuit (low-temperature circuit of cooling system 48 V battery module/high-voltage battery (NT2))

The heating circuit is fed from the engine cooling circuit and can contain, among other things, the following components:

• Heating system heat exchanger
• Stationary heater
• PTC heater booster
• High-voltage PTC booster heater

	Additional basic functions
	Coolant pump, basic function		GF20.10-P-2005A
	Detailed information
	Coolant circuit, detailed information	Engine 608	GF20.00-P-1100A
		Engine 260	GF20.00-P-1100B
		Engine 282	GF20.00-P-1100C
		Engine 264	GF20.00-P-1100D
		Engine 256	GF20.00-P-1100E
		Engine 656	GF20.00-P-1100F
		Engine 654	GF20.00-P-1100G
		Engine 139.9	GF20.00-P-1100H
		Engine 254	GF20.00-P-1100I
		Engine 279	GF20.00-P-1100J
		Engine 176	GF20.00-P-1100K
		Engine 177	GF20.00-P-1100L
		Engine 139.5	GF20.00-P-1100M
		Engine 274	GF20.00-P-1100N
		Engine 177 in model 465.2	GF20.00-P-1100O
		Engine 256 in model 465.2	GF20.00-P-1100P
		Engine 656 in model 465.3	GF20.00-P-1100Q
		Engine 276	GF20.00-P-1100R
		Engine 642	GF20.00-P-1100S