ME engine coolant heat management function

P07.61-3031-79

1 to radiator

2 from engine

3 to engine

18 Oil-water heat exchanger

A1 Instrument cluster

B2/5 Hot film MAF sensor

B11/4 Coolant temperature sensor

B70 Crankshaft Hall sensor

A Full throttle position

B Short-circuit operation position

C Mixed fuel operation position

D Maximum radiator operation position

M4/7 Engine and AC electric suction fan with integrated control

N3/10 ME-SFI [ME] control unit

N22 AAC [KLA] control and operating unit

N47-5 ESP and BAS control unit

Y21 Duovalve

Y110 Three-disk thermostat valve

CAN Data bus

Heat management controls the coolant temperature of the engine. Advantages are

 The operating temperature is reached more rapidly

 Emissions reduced

 Fuel savings up to around 4 %

 Improved heat comfort.

Heat management is dependent on the following input signals:

 Coolant temperature

 Engine load

 Engine speed

 Outside air temperature

 Intake air temperature

 Actuation of the suction fan

 Vehicle speed

 Driver type (quiet or sporty).

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Depending on the operating conditions, the ME control unit actuates the heater element in the three-disk thermostat depending on performance mapping via a ground signal. The voltage is supplied to the three disk thermostat via circuit 87. The coolant temperature is regulated between 80 °C and 100 °C via the duty cycle.



If the coolant temperature is too high, the coolant temperature warning lamp in the instrument cluster is actuated. To do this, the ME control units sends a CAN command to the instrument cluster.

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Full throttle position (A)

For a cold start, the three disk thermostat is not actuated and additionally, when the vehicle heater is shut off, the heater circuit is closed via the duovalve. The standing coolant warms up very quickly. Heat is sent from the engine oil via the heat exchanger at the front of the engine.

At a coolant temperature from around 70 °C or from around 45 °C (with outside temperature above around 12 °C), switching from full throttle to short-circuit operation takes place. In addition, the closing disk opens due to pressure via the running coolant pump over around 3500 rpm.

Short-circuit operation position (B)

Short-circuit operation with the engine and heat exchanger can be throttled so that the heater responds more rapidly.

Mixed fuel operation position (C)

Temperature regulation with the three-disk thermostat is not enabled until the coolant temperature following start reaches around 98 °C. At outside temperatures above around 12 °C it is active immediately.

At partial load, the three-disk thermostat regulates at an increased coolant temperature of around 100 °C.

To prevent critical temperatures, the increased coolant temperature range is reduced under the following conditions to around 90 °C (with outside temperature below 12 °C) or to around 80 °C (with outside temperature over 12 °C):

 Engine speed greater than 3000 rpm

 Engine load more than 30 %

 Intake air temperature more than around 38 °C

 sporty driver detected.

Maximum radiator operation position (D)

The three-disk thermostat is actuated constantly during radiator operation. Above around 110 °C, the three-disk thermostat is always fully opened independently of actuation (emergency operation function).