Method for emptying the pressure medium from a hydraulic unit of a hydraulic brake system of motor vehicles

A method for emptying the pressure medium from a hydraulic unit (34) of a hydraulic brake system (10) of motor vehicles, in which the hydraulic unit (34) has connections (36, 37, 38) for brake lines (13, 14, 15), which lines (13, 14, 15) connect the hydraulic unit to a master cylinder (11) with a pressure medium supply container (12) and also to wheel brakes (16, 17), the hydraulic unit having at least one valve (25), which is actuatable by exertion of magnetic force and which has a removable electrical coil (41), said at least one valve (25), when unactuated, assumes a blocking position, comprising the following method steps:

• removing the electrical coil (41) from the at least one valve (25);
• connecting the hydraulic unit (34) to an air source (46) of adequately high pressure;
• switching the at least one valve (25) to an open position by the exertion of magnetic force from a permanent magnet (48);
• wherein air is carried from an air source (46) through the hydraulic unit (34);
• and
• the pressure medium contained in the hydraulic unit (34) is positively displaced by the air from the air source (46) and caught.