A 2008 TOYOTA corolla car with a mileage of about 106 thousand km, equipped with manual transmission and EPS. Users reflect: the chassis is different, that is, when there is a slightly uneven pavement, there is a "carbazole" from under the chassis, like the iron bump, and the sound should come from under the engine room. Fault diagnosis: the master changed the glue of the front and rear feet (when the glue cracked), the two front shock absorption core (oil leakage), the cushioning rubber (also found broken), the balance rod ball head, the problem was still unsolved. Check left and right swing arms, no loosening, steering wheel tension bar is not loose, bearing and no loose feeling. The fault diagnosis is in trouble. When I took over, I tried the car first. I did find that when the road was slightly uneven, there was a "clicking and carbazole" like the iron bump from under the chassis. There was a phenomenon worth noticing: when the abnormal sound occurred, the steering wheel felt the shock obviously; and when the noise did not happen, the steering wheel was not. Vibrate. Doubt is the problem of the steering machine or the downward axis of the steering machine. The two front wheel of the car is raised, and the front wheel of the car is rocking to the right and left side (the other is called tight). It is found that the gap is not large, and it belongs to the stop range. Using the hand to swing the lower axle of the steering gear from the main driving position, it is found that the clearance is not large. The other parts of the chassis were re examined, and no loose place was found. A sound sensor is set up respectively in the lower shaft of the steering engine, the steering machine and the front axle, and the steering machine, respectively. It is found that the sound is the largest in the vicinity of the lower shaft of the engine, the steering machine and the front axle. The sound sensors can not be collected in the vicinity of the left and right brake pumps, the left and right pendulum, the left and right top rubber, the left and right axes, respectively. At this point, the problem of connecting the steering gear, the lower axle of the steering gear or the steering gear with the front axle is preliminarily judged. Again check the chassis, focus on the front axle of the screws, all check all fastening screws, no screw loose phenomenon, and finally "determine" the noise from the steering machine. In the case of shaking the lower shaft of the steering machine with the hand, there is only a little gap between the left and the right (radial), and when the gap is normal when the front wheel is left and right, whether the source of the abnormal sound is a steering machine is the focus of the debates of the master. I let them discuss the front bridge with the steering machine and check the parts of the front bridge again. There is no doubt, and then the radial clearance of the steering wheel is reloaded and the noise disappears. Fault summary: the abnormal noise caused by the steering machine in this case is very rare, so it takes some time for the diagnosis to use the professional abnormal noise diagnosis equipment. Some diagnostic principles of abnormal sound of the chassis: first, understand the generation of abnormal sound (sound) - the formation of the abnormal sound is vibration or vibration, and then through the air or other media to conduct sound, that is, the first vibration or vibration to produce sound, if the parking when the abnormal sound can be reproduced, then you can use the hand to touch the vibration directly. The sound source is probably known; if it is in the two rounds of the upper and lower pendulum, the brake pad, the brake sub pump, the sound is much larger than the sound heard in the window, and then, if it is the abnormal sound of the balance bar head, the main and pareparant driving position will feel the vibration in the car when the abnormal sound occurs. And the sound is sound, but the sound of the side that produces the abnormal sound is greater; if it is the abnormal sound produced by the horizontal pull rod of the steering machine, grab a front wheel and shake the other wheel, the gap will be larger, and the side that produces the abnormal sound is obvious when the wheel passes the uneven road, and the steering wheel will probably have when the abnormal sound occurs. There is a certain vibration (and the abnormal steering of the bamboo is generally not vibrant or lighter, because the sound of the arms will be weakened by multiple connections and then to the steering wheel); if the inside of the cage is dissimilar, there will be a different noise when you walk on the straight road or at the turn, and sometimes there will be a "carbazole" very crisp. Voice; if the outer cage is abnormal, the sound is most obvious when the steering is basically killed. The abnormal sound is rarely produced and the difficult position of the general technician is the abnormal sound produced by the steering gear shaft due to the loose, which causes the steering wheel to shake obviously, that is, when the abnormal sound occurs, the steering wheel is obviously feeling the vibration in the direction of the abnormal sound, but this sound sounds a lot smaller outside than it is inside. There are two aspects of the broken method: first, when the two windows are lowered, the sound of different sounds from the outside is obviously not sound in the car, and the noise caused by the outer ball or the arm is excluded. After all, the window glass plays a certain sound off function, and the two is when the sound is different. The disc vibrate, with the foot against the lower axle of the steering gear, the abnormal noise is obviously reduced.