It is difficult for ordinary car owners to distinguish between faulty abnormal sound and reasonable abnormal sound. When I went to the garage to check the vehicles with abnormal noise, only nearly 20% of the vehicles really had problems. There must be a difference between the sounds of turbocharged engines and naturally aspirated engines. Vehicles equipped with engine guards may also generate noise due to friction; Some car owners may mistake reasonable abnormal noise for vehicle failure due to their ignorance of mechanical knowledge after contacting different cars. Therefore, learn to distinguish the abnormal sound of cars and avoid wasting time and energy.
Second, the identification method of automobile noise:
In practical work, due to the limitation of working conditions, it is difficult to measure automobile noise with special instruments, and we can only describe and compare automobile noise by judging the sound in daily life. For example, the "click" sound produced by dry friction of bearings, and the "click" sound similar to a small hammer hitting the cement floor caused by excessive valve clearance.
1, correctly distinguish normal noise from abnormal noise.
When the car is working, the vibration of various mechanisms will make various noises, but the noise does not mean that the car is faulty. In order to avoid unnecessary disassembly, it is necessary to distinguish normal noise from abnormal noise. The normal vibration sound of each system component (such as the noise on the engine surface), the impact sound of gears during gear shifting, the intake and exhaust sound with gas as the working source, and the gear meshing noise are all normal noises. Abnormal noise can be divided into slight noise, general noise and malignant noise according to its influence on automobile performance. Slight noise, such as high voltage leakage flashover noise, slight looseness noise of rolling bearing, etc. Generally, the volume is low, the wear degree of parts is not great, and there is no obvious change for a long time. This kind of fault can maintain the normal running of the car without repair.
3, in the diagnosis of abnormal car noise, should pay attention to create good auscultation conditions, try to eliminate the interference of other noise, so as not to affect the accuracy of judgment.
It is best to amplify or reduce the sound consciously, that is, to use a screwdriver or other metal bar as the sounding part of the stethoscope to amplify the sound, or to use a single tube to cut off the fire to reduce the sound to meet the needs of diagnosis. The auscultation site should be kept quiet to minimize the interference of human factors.
Thirdly, let's list some common and easy-to-eliminate automobile abnormal noises and simple methods of identification and elimination.
1, abnormal car body noise.
Symptoms: When you step on the accelerator or brake while driving, there is always some abnormal noise in a certain part of the car body, which is not loud and does not affect the normal driving, but it always makes people a little worried about what the problem is.
Analysis: This kind of problem usually occurs because the rigidity of the car body is not enough, which leads to the deformation of the vehicle during driving, friction or jitter between the door and the frame, or friction between the steel plates due to the off-welding in some places.
There are also some cars that are noisy, which is related to the shape of the car to some extent. There are also some cars whose body parts are not fixed well, which may also produce abnormal noise, which can generally be solved by tightening the screws.
Solution:
First of all, check whether there are any items in the trunk or back seat of the car that are not fixed, easy to roll and make noise, and eliminate the noise caused by some items that are not fixed.
If it is found that abnormal noise is caused by the friction between doors and windows, rubber strip can be affixed to doors and windows, or rubber can be put on the friction parts, which may reduce or eliminate abnormal noise, but the result is only a temporary solution, not a permanent cure. If the above problems are not found, you must go to a regular repair shop for maintenance and troubleshooting.
2. The engine has abnormal noise.
Symptom description: There is a high possibility of abnormal noise in the engine compartment. Most people also judge the abnormal noise in the engine compartment according to the sound source, usually the harsh noise of metal or the noise of the wind whistling.
Problem analysis: abnormal noise in the engine compartment will lead to harsh belt howling, which is generally caused by belt slipping; When the engine is running, there will be sharp sound of dry friction of metal parts, which is generally the cause of bearing damage of generator, water pump and steering booster pump; If it is the sound of air leakage during engine operation, it may be the result of blockage of exhaust system, air leakage or fracture of vacuum tube.
Solution: The abnormal sound of the engine indicates that the technical state of a certain mechanism of the engine has changed. The main reason is that some parts are worn or even improperly adjusted. Some abnormal sounds can indicate that the engine may be accidentally damaged, so when the engine has abnormal sounds, it should be repaired in time to prevent the fault from expanding.
Need to be reminded that if the engine is abnormal, most owners can't solve it by themselves, so it's best to send it to the factory for maintenance.
3. The gearbox has abnormal sound.
Symptoms: If there is a "rustling" sound inside the gearbox when the car is driving, but it disappears after stepping on the clutch or accelerator, there will be a whistle when shifting gears.
Analysis problem: If the noise source encountered during driving is the gearbox, it may be caused by the wear of gearbox bearings or gear and bearing spots. The abnormal sound of the gearbox during the speed-up shift may be caused by the metal powder contained in the gearbox oil, indicating that the brake band clutch and other parts in the gearbox are excessively worn.
4. The tire has abnormal sound.
Description of symptoms: The tires make rhythmic noises. The faster the vehicle speed, the higher the frequency.
Analysis: When an automobile tire touches the ground, various noises with different intensities will be generated due to the different types of roads or concave and convex states, the speed of the automobile, the types of tires and the air pressure of the tires themselves. Therefore, no matter how perfect the car is, it can't completely eliminate the noise generated by tires and the ground during driving.
5. The engine guard has abnormal sound.
Symptoms: The engine fender has been installed for some time, but after going out to run some suburban road conditions, there is strange noise at the fender when I come back.
Solution: the car that moves frequently, the screw often moves. If you often hear abnormal noise similar to "rattle" from the position of the air intake grille, besides the grille is really loose, then the owner should check whether the engine fender screw is loose, or whether the engine fender and the negative film are loose, resulting in abnormal noise. In addition to tightening the screws, you should also pad some cardboard items at the abnormal sound position, so that the abnormal sound can be easily eliminated.
6. The brakes are abnormal.
Symptoms: The vehicle makes a lot of noise and abnormal sound when stepping on the brakes.
Analysis: Of course, abnormal noise during braking may also be caused by other reasons, such as improper use or deformation of brake disc materials, hardness and porosity of brake friction plates, etc.