Abstract: In order to find out the reasons of the high coolant temperature performance of a light truck, combined with customer vehicle driving status and test on chassis dynamometer, comparative testing using the hub test method with precise control of boundary conditions. Analyzes the difference between engine load, fan state and thermostat state. The conclusion is that the thermostat can not be turned on in time in winter. Through simple on-site measures, the water temperature of the fully open thermostat was verified, and it was determined that the vehicle thermostat could not be opened in time in winter, so that the water temperature gauge indicated that the water temperature in winter was higher than that in summer. This conclusion can provide test support for engine product development, and remind the engine development process to pay attention to the verification of the timing of the engine thermostat opening under low load conditions.

Key words: Light truck; High coolant temperature; Analyses; Test support; Low load condition

摘要： 为了锁定市场反馈的某轻型卡车整车水温表现偏高问题的根源，结合客户车辆道路行 驶过程中的相关数据对车辆行驶状态进行分析，利用可精确控制边界条件的转毂试验方法进 行对比测试。重点从发动机负荷、风扇状态、节温器状态等影响发动机水温的参数入手，对 开发试验结果与复测结果进行差异对比分析，发现节温器不能及时开启。通过现场简易措施， 验证全开式节温器状态的水温，判定车辆节温器冬季不能及时开启导致冬季水温表指示水温 高于夏季。此结论可以为发动机产品开发提供试验支持，提醒发动机开发环节，需要注意在 低负荷条件下发动机节温器开启及时性的验证。

关键词: 轻型卡车；整车水温偏高；分析验证；整改验证；优化设计