BMW 5 Series Owners & Service Manuals

BMW 5 Series: 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 of the heat management module
Cold-start phase, Bx8TU engine

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

Operating strategy of the heat management module
Warm-up phase, Bx8TU engine

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 electric split cooling valve is closed; no coolant flows through the engine block (split cooling).


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