Hydraulic brake valve and a method of bleeding a hydraulic brake system

A hydraulic brake valve (10) comprising a body (12), a passageway (14) defined in the body, an inlet (16) to the passageway, an outlet (18) from the passageway and a movable valve member (20) in the passageway, said valve member having a first condition blocking the passageway to prevent communication between the inlet and the outlet, and a second condition wherein the valve member is adapted to maintain the passageway open to allow communication between the inlet and the outlet in response to a pressure differential exceeding a predetermined value, the valve member remaining in its second condition once it has been moved to its second condition. A hydraulic brake valve of this kind may be used in a method for vacuum bleeding a hydraulic servo brake.