To bleed the brakes, you will need an assistant. If you need to bleed the entire system, you should do this separately for each of the calipers. If air has gotten into only one of the calipers, it is enough to bleed this caliper.
Bleeding sequence: 1) rear left caliper, 2) rear right caliper, 3) front left caliper, 4) front right caliper.
Remove the dust cover from the brake cylinder drain valve. Clean the valve and put a clean tube on it. Lower the other end of the tube into a container half filled with brake fluid.
Ask an assistant to press the brake pedal several times to build up pressure in the brake system (each time you press the brake pedal you will feel more and more resistance).
After creating pressure in the system, press the brake pedal all the way down and hold it in this position.
Using a spanner, open the drain valve about half a turn and collect the spilled liquid in a container. Make sure that the end of the tube is always below the surface of the liquid.
After the liquid stops flowing, close the drain valve.
Re-pressurize the system by pressing the brake pedal. Press the pedal and, holding it in this position, open the drain valve and let the fluid drain, then close the valve again.
Repeat this procedure on one cylinder until the flowing fluid no longer contains air bubbles.
Remove the tube from the drain valve and put the boot on it.
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Repeat the above operations on the remaining brake cylinders.
Caution: When bleeding the brakes, constantly monitor the fluid level in the brake reservoir. Do not let it drop too much, as this may allow air to enter the system. Always use fresh brake fluid for topping up.
After bleeding the system, the tank should be filled to the "max" mark.