Recommendation. If the brake system is in good condition and no air has entered the hydraulic drive, do not drain all the old fluid from the system. It is more correct to replace the fluid, displacing it with a new fluid. Also, to reduce the time to complete the work, the maximum possible amount of old fluid should be taken from the reservoir of the main brake cylinder with a rubber bulb or syringe.
Without starting pumping, fill the reservoir with new brake fluid. We pump each circuit of the working brake system until new brake fluid begins to come out of the fittings (she is lighter).