1　概述　　东风4Ｂ型机车是哈密机务段担当敦煌至鄯善货运任务的主要机型。近年来 ,该机型曲轴箱超压故障发生较多 ,给运转乘务员途中判断、检修人员查找原因带来了困扰。为解决该问题 ,我们从多角度对该故障进行了分析 ,并总结了查找方法。2　故障原因分析　　曲轴箱超压故障 1 Overview The DF-4B locomotive is the main model of the Hmong depot that serves as the cargo transporter from Dunhuang to Shanshan. In recent years, the model crankcase overpressure fault occurred more, to run the flight attendants to determine the way, maintenance personnel to find the cause of trouble. To solve this problem, we analyzed the fault from multiple perspectives and summarized the search methods. 2 Analysis of the cause of the failure of the crankcase overpressure