Process for operating a hydraulic brake system

A method of operating a hydraulic brake system which is equipped for active braking and includes the following components:

• a pedal-operated master cylinder which is connected to a supply reservoir and supplies fluid to at least one brake circuit by way of a brake line to which at least one wheel brake is connected,
• a low-pressure accumulator which is connected to the wheel brake by way of a return line,
• a self-priming return pump which has a connection to the low-pressure accumulator via a first suction line and to the brake line via a second suction line, and the pressure side of the pump being connected by a pressure line to the brake line between the connections of the second suction line and the wheel brake,
• a separating valve in the brake line between the connections to the second suction line and the pressure line,
• an inlet valve in the brake line between the connections of the pressure line and the wheel brake,
• an outlet valve in the return line,
• an electrically operated change-over valve in the second suction line, the said electrically operated change-over valve being opened during active braking operations in case of a requirement of additional brake fluid,
• wherein the requirement is determined by evaluating at least one quantity out of the group consisting of rotational speed and current consumption of the drive motor of the return pump.