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

Engine 264.9 in Model 205, 253 

Function requirements, general 

IMPORTANT The ME-SFI [ME] control unit (N3/10) detects the Engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] control unit directly reads in the signals of the crankshaft Hall sensor.

Thermal management, general 

The ME-SFI [ME] control unit regulates the Engine coolant temperature via the heat management.

The following advantages arise from this:

The ME-SFI [ME] control unit reads in the following signals to the control the heat management:

The ME-SFI [ME] control unit also evaluates the following variables:

G14180759Courtesy of MERCEDES-BENZ USA

Schematic diagram of cooling circuits (with code B01 (48V Technology)) 

The thermal management is described in the following points:

Display of coolant thermostat connections 

G14180760Courtesy of MERCEDES-BENZ USA

Coolant thermostat closed-loop control 

The mechanically influenced opening and closing of the ball rotary valve in the coolant thermostat takes place via the temperature-dependent expansion or contraction of the wax expansion element in a temperature range of approx. 102 °C to 118 °C. Target temperature is approx. 105 °C. At 118 °C, the ball rotary valve is fully opened.

The opening and closing of the coolant thermostat can also be electronically influenced by the actuation of the coolant thermostat heating element. This occurs fully variable and dependent on the motoric requests.

The ball rotary slide in the coolant thermostat can take the following positions:

View of coolant thermostat closed 

G14180761Courtesy of MERCEDES-BENZ USA

Closed 

The coolant thermostat's annular slide valve (12) is closed when the following conditions are met:

In this position the coolant flows through the Engine circuit and the heater heat exchanger and the ATL and, as required, the heater heat exchanger for the passenger compartment heater. The Engine radiator is not integrated in the coolant circuit. The coolant is heated more quickly in this way.

Through rapid warming the Engine reaches its operating temperature quicker which is favorable for fuel consumption.

View of the coolant thermostat opened 

G14180762Courtesy of MERCEDES-BENZ USA

Open (mixed-fuel mode) 

The annular slide valve (12) starts to open when one of the following conditions is met:

At a coolant temperature range of approx. 102 °C to 118 °C or depending on the energization of the coolant thermostat heating element, the wax expansion element (13) begins to expand and actuates the annular slide valve (12). This opens the connection to the Engine radiator. The orifice area of the annular slide valve (12) is proportional to the temperature of the expanding wax element (13) or the coolant temperature. In this way the volumetric flow rate of coolant to the Engine radiator can be varied as required.

Open (radiator operation) 

Upon reaching a coolant temperature of approx. 118 °C, the annual slide valve (12) is completely open and the coolant can flow through the radiator without restriction.

Electronic regulation 

A complete opening is also possible at lower temperatures, if the coolant thermostat heating element is actuated by the ME-SFI [ME] control unit depending on the operating conditions.

The following data are read in directly by the ME-SFI [ME] control unit:

The compressor is actuated via a ground signal. The power supply takers place over "circuit 87 M2".

Dependent on the motoric requests, a higher or a lower coolant target temperature is adjusted.

For a high specified coolant temperature (approx. 105 °C), the mechanical regulation is support by additional heating of the wax expansion element (13) as of 106 °C. The coolant thermostat heating element is fully energized at 110 °C, which results in the full opening of the ball rotary valve. An increased coolant temperature produces in partial-load range a favorable performance level, which works very positively on the fuel consumption.

The low specified coolant temperature is approx. 85 °C. In this case, the coolant thermostat heating element is subject to pilot control, which is variably adapted to the ambient conditions. In summer and at high outside temperatures, the coolant thermostat heating element can already be fully energized at 80 °C in order to avoid critical temperature ranges. In winter and at low outside temperatures, the coolant thermostat heating element is energized with 30 to 50 % of the maximum output.

A low coolant temperature in the wide open throttle operation has a positive effect on the Engine power, since the intake air is less warmed.

Post-start phase with electric coolant pump 

In the post-start phase the coolant circulation stopped through cutting out of the electrical coolant pump. Due to missing cooling the Engine warms quicker and the exhaust emission are reduced.

The electric coolant pump is switched off for a cold start if the following conditions are fulfilled:

The electrical coolant pump switches on in response to the request "Heat'. In this way the FIR is heated quickly.

If the conditions for shutoff of the electric coolant pump are no longer fulfilled, the ME-SFI [ME] control unit stops actuation of the electric coolant pump. The coolant circulation is therefore achieved again.

Starter-alternator cooling (with code B01 (48V Technology)) 

The starter-alternator is connected, together with the transmission oil heat exchanger for cooling, to the high temperature circuit. To prevent a heat buildup in the high temperature circuit, the coolant is also circulated by the starter-alternator coolant pump or coolant pump 2.

The ME-SFI [ME] control unit actuates the starter-alternator coolant pump or coolant pump 2 in a demand-dependent manner from 0 to 100 % via the Engine LIN based on the following signals:

Low-temperature circuit 1 (charge air cooling) 

The liquid-cooled charge air cooler is connected to the low-temperature circuit 1.

The coolant in low-temperature circuit 1 is circulated to prevent overheating at specific points in the circuit. To do this, low-temperature circuit circulation pump 1 is regulated by the powertrain control unit in a demand-dependent manner via the drivetrain LIN (LIN C3).

The regulation depends on the following variables:

Low-temperature circuit 2 (with code B01 (48V Technology)) 

The DC/DC converter control unit and the 48 V on-board electrical system battery are cooled via low-temperature circuit 2. The coolant in low-temperature circuit 2 is circulated by low-temperature circuit circulation pump 2.

The powertrain control unit regulates low-temperature circuit circulation pump 2 in a demand-dependent manner via the drivetrain LIN depending on the coolant temperature in low-temperature circuit 2. To do this, the powertrain control unit reads the low-temperature circuit 2 temperature sensor signals in directly.

Overheating protection 

The overheating protection protects the Engine and catalytic converter against damage due to thermal overload.

In the case of an imminent thermal overload, the ME-SFI [ME] control unit initiates the following measures:

Fan control 

The powertrain control unit actuates the fan motor (M4/7) via the drivetrain LIN in an output-controlled manner between 0 and 100 %. In the event of faulty actuation, the fan motor turns with maximum Engine speed (fan emergency mode).

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.

Radiator trim flaps (with code 5U3 (AIRPANEL)) 

The radiator trim flaps are close in order to lower the fuel consumption (thorough having 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 flaps are opened under the following preconditions:

The radiator trim flaps are closed when the conditions are no longer fulfilled or the Engine is off. The powertrain control unit actuates the radiator trim flap actuator motor (M2/37) via the powertrain LIN.

IMPORTANT Limp-home function:

In the event of a malfunction, the radiator trim flaps are opened abruptly with a noticeable noise by the spring preload of the radiator trim flap actuator motor.

IMPORTANT Cleaning position:

Switch on ignition (the Engine may not be switched on). The radiator trim flaps open automatically after approx. 120 seconds.

Radiator shutters (with code 2U1 (Radiator shutters)) 

The radiator shutters is closed in order to lower the fuel consumption (thorough having 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 shutters are opened under the following conditions:

The radiator shutters are closed under the following conditions:

The powertrain control unit actuates the radiator shutters actuator motor (M87) via the drivetrain LIN.

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