Motor pump unit

A motor pump unit comprising:

• a housing enclosing a first chamber and a second chamber communicating with each other in the housing, said first and second chambers defining a common oil reservoir;
• an electric motor having a motor shaft within said housing;
• at least one radial piston pump arrangement provided within said first chamber and drivable by said motor shaft;
• a separation wall between said first and second chambers;
• means for supplying pressurized oil to said first chamber;
• and
• a filling and pressure biasing system associated with said first chamber and including a pre-biasing valve located in an oil outlet channel of said first chamber for inhibiting a flow of the oil supplied to said first chamber via said pressurized oil supply means until a pre-selected oil level and a pre-selected pre-biasing oil pressure are reached in said first chamber, and allowing flow of oil out of said first chamber through said outlet channel only when said predetermined oil level and said pre-selected prebiasing pressure are maintained in said first chamber during operation of the motor pump unit,
• said oil level and said biasing oil pressure being pre-selected such that said radial piston pump arrangement is supplied with oil substantially without any air entrapped in the oil during operation of said motor pump unit.