BMW B58TU Reference Manual page 30

B58TU￿Engine
4.￿Cooling￿System
4.4.￿Coolant￿pump
The￿layout￿and￿function￿of￿the￿coolant￿pump￿have￿been￿revised￿and￿adapted￿to￿match￿the￿cooling
concept￿of￿the￿Bx8 TU engines.
Coolant￿pump,￿Bx8TU￿engine
Index
A
B
A￿pressure￿relief￿valve￿is￿installed￿in￿the￿mechanical￿coolant￿pump￿housing.￿In￿combination￿with￿the
heat￿management￿module,￿the￿pressure￿relief￿valve￿on￿the￿one￿hand￿ensures￿that￿the￿engine￿operating
temperature￿is￿reached￿more￿quickly,￿while￿at￿the￿same￿time￿reducing￿leaks￿and￿component￿damage
due￿to￿high￿pressure￿in￿the￿cooling￿system.
If￿an￿excess￿pressure￿of￿more￿than￿2.1 bar￿builds￿up￿in￿the￿coolant￿circuits,￿the￿pressure￿relief￿valve
opens￿and￿releases￿a￿bypass￿channel.￿The￿coolant￿is￿now￿exclusively￿circulated￿in￿the￿pump￿body.
Once￿the￿pressure￿drops￿below￿2.1 bar￿or￿the￿engine￿speed￿rises￿above￿3000￿rpm,￿the￿pressure￿relief
valve￿closes￿and￿the￿coolant￿is￿again￿routed￿through￿the￿engine's￿coolant￿ducts.
Explanation
Pressure￿relief￿valve￿closed￿(pressure < 2.1 bar)
Pressure￿relief￿valve￿opened￿(pressure > 2.1 bar)

25