ME engine coolant heat management function - GF07.61-P-4016AMG

ENGINE 156.980 in MODEL 164, 251 up to Model Year 8 

ENGINE 156.982 in MODEL 209 

ENGINE 156.983 in MODEL 211, 219 

ENGINE 156.984 in MODEL 216, 221 up to Model Year 8 

Fig 1: Identifying ME Engine Coolant Heat Management Function Diagram

Courtesy of MERCEDES-BENZ USA

Heat management controls the coolant temperature of the engine.

Advantages are

• Operating temperature is reached faster
• Reducing exhaust gas emissions
• Better mixture formation for partial load
• Fuel saving
• Better heating comfort

Heat management is dependent on the following input signals:

• Coolant temperature
• Oil temperature
• Engine load
• Engine speed
• Outside air temperature
• Intake air temperature
• Vehicle speed
• Driver type (quiet or sporty)

1. Thermostat control 

   The temperature of the coolant can be controlled variably by means of the heatable two-disk thermostat. The two-disk thermostat has a heating element for this purpose which is energized according to need by the ME-SFI [ME] control unit. Heating of the two-disk thermostat opens this and the coolant is led through the engine radiator (cooler operation).

   In order to achieve optimum in-engine friction and this fuel saving the coolant temperature can be raised to about 100°C in partial-load range (heating element deenergized - short-circuit operation). The friction power drops due to a higher oil temperature and the mixture formation is improved due to less fuel condensation on the cylinder barrels.

   At full load the two-disk thermostat can be opened very rapidly (radiator operation) through heating (heating element energized). The coolant temperature can be lowered in the process to about 85°C whereby the best possible engine cooling and knock-free combustion is achieved.

   Short-circuit operation position (A) 

   Heating element deenergized Coolant temperature <100°C

   Heating element energized Coolant temperature <60°C

   Mixed fuel operation position (C) 

   Heating element deenergized Coolant temperature 100 to 115°C

   Heating element energized Coolant temperature 60 to 100°C

   Radiator operation position (C) 

   Heating element deenergized Coolant temperature >115°C

   Heating element energized Coolant temperature >100°C

   Above about a 115°C coolant temperature the two-disk thermostat is fully open independently of energization (limp-home function).

2. Heating system 

   In order to achieve more rapid heating of the engine shutoff of the coolant circuit for the heating system occurs by means of the heating system shutoff valve.

3. Fan control 

   The ME-SFI [ME] control unit indirectly actuates the electric suction fan engine and AC. The request for the specified fan speed for AC operation is received by the ME-SFI [ME] control unit from the comfort AAC [KLA] control and operating unit via the CAN data bus.

   The fan specified speed is transmitted by the ME control unit via a pulse width modulated signal (PWM signal).

   The duty cycle of the PWM signal is 10 to 90 %.

   Meaning:

   10% Electric suction fan "OFF"

   20% Electric suction fan "ON", minimum speed

   90% Electric suction fan "ON", maximum speed

   If the actuation is faulty, the electric suction fan rotates with maximum rotational speed (fan emergency mode).

4. Engine oil cooling (for model 164, 216, 221, 251) 

   The cooling circuit of the engine oil cooling takes place via the engine oil cooler and engine oil heat exchanger.

   The engine oil temperature is detected by the ME-SFI [ME] control unit by the oil temperature sensor. At a high oil temperature the ME-SFI [ME] control unit actuates the engine coolant circulation pump via the engine coolant circulation pump relay. This pumps coolant from the engine cooling circuit through the engine oil heat exchanger.

5. Engine oil cooling (for model 209, 211, 219) 

The cooling circuit of the engine oil cooling takes place via the engine oil cooler and additional engine oil cooler. The engine oil temperature is detected by the ME-SFI [ME] control unit by the oil temperature sensor. At a high oil temperature the ME-SFI [ME] control unit actuates the oil cooler fan via the oil cooler fan relay (except for model 209 with code P98 Black Series).