当真空伺服机构出现故障时，可按逐段检查法逐级检测故障点；有时判定性界定某总成是否损坏，可单选检查。
When the vacuum servo mechanism fails, the fault points can be detected step by step by step according to the method of step inspection. Sometimes, the deterministic definition of whether an assembly is damaged or not can be checked optionally.
①真空源检查拆去伺服机构气路与汽油机的真空接头或真空泵接头，起动发动机，观察接在接头上的真空表的指针在一定时间内能否迅速达到标定值，且指针摆动是否稳定，从而判定真空源是否有故障。若汽油机原怠速飘移，此时运转正常，则可认定伺服机构存在漏气现象。
(1) The vacuum source inspects and dismantles the vacuum joint or vacuum pump joint of the servo mechanism and the gasoline engine, starts the engine, observes whether the pointer of the vacuum meter connected to the joint can quickly reach the calibration value within a certain period of time, and whether the pointer swings steadily, so as to determine whether the vacuum source has a fault. If the gasoline engine drifts at idle speed and works normally at this time, it can be concluded that there exists air leakage in the servo mechanism.
②在未制动状态下查排故障点在气路系统取得真空源后，在单向阀（逆止阀）后接装真空表，若真空表指针不回落，则说明管路、真空筒和助力器（增压器）控制部分完好；若真空表指针回落，则说明上述部件有漏气处。为确定漏气部位，应逐段进行检查
(2) After the vacuum source is obtained in the air circuit system, the vacuum meter is installed after the one-way valve (check valve). If the pointer of the vacuum meter does not fall back, the control parts of the pipeline, the vacuum cylinder and the booster (supercharger) are in good condition; if the pointer of the vacuum meter falls back, the parts mentioned above have air leakage. In order to determine the location of air leakage, the inspection should be carried out step by step.