故障现象一辆行驶里程约为21万km的2006年产上海大众帕萨特轿车,起动时发动机有异响。故障诊断接车后打开发动机室盖并起动车辆,立即听到发动机发出较响的“当当”声,传出声音的部位位于发动机前侧。根据该声音特征及部位,初步判断是正时带轮附近的机械故障,但具体产生异响的部位仍需进一步确定。按照从简到繁原则,将发动机熄火后先拆除了发动机正时带,然后重新起动,异响依然存在,说明不是正时带方面的问题;再将发动机熄火,拆除曲轴扭转减振器,起动发动机,异响消失,从此判定故障应该在曲轴扭转减振器方面。该车使用的是橡胶扭转减振器(图1),拆开后发现硫化 Symptom A mileage of about 210,000 km production of the Shanghai Volkswagen Passat sedan, the engine started a strange sound. Troubleshooting After the car is taken over, open the engine room cover and start the vehicle, and immediately hear the sound of “Dangdang” sounded by the engine. The part where the sound comes from is located on the front side of the engine. According to the sound features and parts, the initial judgment is a mechanical fault near the timing pulley, but the specific site of abnormal sound still need to be further identified. In accordance with the principle from simple to complex, the engine flameout after dismantling the engine timing belt, and then restart, abnormal sound still exists, indicating that the timing belt is not the problem; then turn off the engine, remove the crankshaft torsional vibration damper, start the engine , Abnormal noise disappeared, judging from the fault should be in the crankshaft torsion damper. The car uses a rubber torsional vibration absorber (Figure 1), opened and found vulcanized