BMW 3 Owners & Service Manuals

BMW 3: Operating strategy

The following graphic shows the positions of the rotary valve as the coolant temperature increases:

Operating strategy
Switching diagram heat management module

0% - Rotary valve closed
100% - Rotary valve open

  1. Cold start
  2. Warm-up phase
  3. Operating temperature
  4. Transition from normal operation to maximum cooling requirement
  5. Maximum cooling requirement

X - Rotational angle in angular degrees

  1. Heater circuit
  2. Main coolant circuit
  3. Minor coolant circuit

The openings on the rotary valve vary the cross-sections of the different coolant ducts as a function of the rotational angle of the rotary valve. The following graphics schematically represent the various engine operation phases, from cold start to maximum cooling requirement.

Cold-start phase

Point A in the heat management module circuit diagram designates the cold start with an engine that has completely cooled down.

Operating strategy
Cold-start phase

In the cold-start phase, the coolant circulates exclusively via a bypass in the coolant pump. The rotary valve in the heat management module closes the coolant lines so that the excess pressure that builds up opens the pressure relief valve in the coolant pump (opening pressure 2.2 bar) and the coolant is recirculated in the coolant pump.

Because the coolant circuits through the exhaust turbocharger and the ventilation line of the cylinder head cannot be closed, a low volumetric flow is returned to the coolant pump here.

Warm-up phase

Area A in the circuit diagram for the heat management module shows the opening angle of the rotary valve in the warm-up phase.

Operating strategy
Warm-up phase

In the warm-up phase, the heat management module additionally opens the connection to the heating in addition to opening the bypass line. The coolant flows through the cylinder head, the exhaust turbocharger and the engine oil/coolant heat exchanger. The electrical Split Cooling Valve is closed; no coolant flow through the engine block (Split Cooling).


     Operating temperature

    The positions of the rotary valve at engine operating temperature are shown by area C of the heat management module circuit diagram. Operating temperature The graphic shows control with the engine a

     Coolant pump

    The layout and function of the coolant pump have been revised and adapted to match the cooling concept of the B46TU/B48TU engines. Coolant pump Pressure relief valve closed (pressure <

     Exhaust System

    Exhaust turbocharger Exhaust turbocharger The exhaust turbocharger can be replaced individually and is exclusively made of steel. The boost charge pressure is still controlled by an electrical waste


     Speed Limit Info

    Speed Limit Info Concept Speed Limit Info shows the currently valid speed limit in the instrument cluster and, if necessary, the Head-up Display. General information The camera in the area of the interior mirror detects traffic signs at the edge of the road as well as variable overhead sign posts.


    Refueling Fuel cap 1. To open the fuel filler flap, press on the rear edge, arrow. The fuel filler flap opens. 2. Turn the fuel cap counterclockwise. 3. Place the fuel cap in the bracket attached to the fuel filler flap. Gasoline For the best fuel efficiency, the gasoline should be sulfur-free or

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