If your brake fluid reservoir is empty, there is “air” in the system. It is necessary to bleed the system after changing the brake pads. This is best done with a helper. One presses the pedal several times and continues to press without releasing, and the second at this time opens the bleed nipple on the brake support, as the pressure drops, close the nipple and then pump the brake pedal again.It is necessary to pump over strictly cross to cross. the system is made in such a way that the right rear wheel works in parallel with the front left wheel. There is also one unpleasant feature in the form of a tee with valves (from where all the tubes diverge) in this tee there are valves that wear out and interfere with pumping the system using a pedal, for good pumping with sticking valves it is possible only on special equipment.
since we basically do everything ourselves, and the tools and equipment are basically either we make ourselves or buy cheap analogs. In general, if you need to pump the system alone and in almost the same way as it is done on special equipment, then you can simply buy a huge plastic syringe (200 ml) to pour in the brake fluid there, put a tight tube on the fitting, open the fitting and force the brake fluid in about 75 ml WITHOUT STOPPING. and without stopping to press, close the fitting. If everything is in order with the valves, then it will be pumped in 1 time (on each side). If not, then change this tee to a new one. GM 96349945