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Thermal Management, Function - GF07.10-P-1012MND

Engine 276.8 in model 213, 238 

up to model year 2021 

Function requirements for thermal management, general points 

Thermal management, general 

The coolant temperature of the engine is regulated with the thermal management controlled by the ME-SFI [ME] control unit (N3/10). The following advantages arise from this:

Thermal management controlling is dependent on the following sensors and signals:

Function sequence for thermal management 

The thermal management is described in the following points:

Function sequence for heating the two-disk thermostat 

The temperature of the coolant can be controlled variably by the heatable two-disk thermostat. There is a coolant thermostat heating element (R48) in the two-disk thermostat which is actuated a required by the ME-SFI [ME] control unit using a ground signal. The two-disk thermostat can take four positions:

G13770184Courtesy of MERCEDES-BENZ USA

Positions of two-disk thermostat 

Position for full throttling 

The coolant thermostat is closed.

Position for short circuit mode 

According to the meaning of optimal in-engine friction and therefore fuel saving, the coolant temperature can be increased to about 105°C in partial-load range (heating element de-energized).

Therefore the friction power can be improved due to a higher engine oil temperature and the mixture formation improved due to less fuel condensation on the cylinder barrels.

Position for mixed-fuel mode 

Position for radiator operation 

Through heating the two-disk thermostat (heating element energized) opens this and the coolant is led through the engine radiator.

For wide open throttle the two-disk thermostat is very quickly opened. The coolant temperature can be lowered to about 80°C whereby best possible engine cooling and knock-free combustion are achieved.

IMPORTANT Above an about 115°C coolant temperature the two-disk thermostat is always fully open independent of the flow rate through the heating element (limp-home function).

Function sequence for fan control 

The powertrain control unit actuates the fan motor (M4/7). In doing the actuation takes place over the drivetrain LIN (LIN C3) and all rotational speeds can be set between 0 and 100 %.

For faulty actuation the fan motor rotates at its maximum rotational speed (fan emergency mode).

The climate control unit send the status of the A/C via the interior CAN, electronic ignition lock control unit, chassis FlexRay to the powertrain control unit and via the drive train CAN to the ME-SFI [ME] control unit.

Delayed fan switch off 

After "ignition OFF", the fan motor continues to run for up to 6 min if the coolant temperature or engine oil temperature has exceeded the specified maximum value. If the battery voltage drops down a lot, the delayed fan switch off is suppressed.

Function sequence for overheating protection 

In case of thermal overload, the overheating protection protects against engine damage and overheating damage to the catalytic converters (three-way catalytic converters).

In the case if an excessively high coolant or intake air temperature the throttle valve of the throttle valve actuator (M16/6), is no longer fully opened by the ME-SFI [ME] control unit dependent on the engine RPM and load. The ME-SFI [ME] control unit shortens the injection period of the fuel injectors (Y76) according to the lower air mass. Furthermore the heating element in the coolant thermostat is actuated by the ME-SFI [ME] control unit so that the two-disk thermostat is fully opened and the whole coolant is cooled over the engine radiator. If the coolant temperature is too high, a warning message in instrument cluster (A1). To do this the ME-SFI [ME] control unit transmits a corresponding signal via the drive train CAN, powertrain control unit, chassis FlexRay, electronic ignition lock control unit and via the user interface CAN to the instrument cluster.

Function sequence for radiator trim flap (for CODE 5U3 (AIRPANEL)) 

The radiator trim flap is closed in order to lower the fuel consumption (by producing a lower aerodynamic drag). This also causes reduced engine compartment cooling off and a dampening of engine external noise emissions to the outside.

The radiator trim flap actuator motor (M2/37) is actuated by the powertrain control unit via the drivetrain LIN after the engine start. For achieving a coolant temperature of 111°C the radiator trim flap is opened and closed again for 99°C.

  Electrical function schematic for heat management   PE07.10-P-2712-97DBF
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