The exhaust gas is similar to that of a car. Fill the oil cup with brake oil and start pumping enough air pressure. It takes two people to cooperate. Each brake assembly has two exhaust bolts, one in the lower row and one in the upper row. One person steps on the brake (don't loosen it), and one person loosens the brake exhaust bolt, and then tightens and loosens the brake pedal. Then, repeat the above steps (observe the amount of oil in the oil cup at any time, and fill it up when it is insufficient), then brake to exhaust and tighten it ... until no air is exhausted. Simply empty the brake assemblies one by one. Finally, fill the pipeline with brake oil and check the oil quantity regularly.