There are many reasons for brake failure. First, there is a lack of necessary maintenance of the brake system. There are too many impurities in the brake master cylinder and the sealing is not tight. The vacuum booster pump fails. The brake oil is too dirty or several types of brake oil are mixed and heated. Air lock occurs in the brake master cylinder. Or the sub-pump leaks oil, the gas storage tank or the pipeline interface leaks. The second reason is due to improper operation.