After major maintenance, the car has abnormal noise, and I don t know what the problem is

The gap between the piston and the cylinder wall is too large; The piston pin assembly is too tight or the connecting rod bearing assembly is not too tight; The gap between the tappet and its guide hole is too large; The air distribution cam profile is worn.

On the issue of abnormal noise of automobiles, it is difficult for ordinary car owners to distinguish which ones are abnormal noises and which ones are reasonable abnormal noises. Only nearly 20% of the vehicles that went to the repair shop to detect abnormal noises really had problems. Equipped with a turbocharged hairstyle, there is bound to be a difference between the sound and the sound of a naturally aspirated engine; Models with engine guards may also make noises due to friction; After some car owners come into contact with different cars, it is likely that due to their lack of understanding of mechanical knowledge, they mistake reasonable abnormal noise as a vehicle failure.

Therefore, learn to distinguish the abnormal noise of the car and avoid wasting time and energy.

How to identify the sound of a car:

In practice, due to the limitations of working conditions, it is difficult to measure the sound of the car with special instruments, and the sound of the car can only be described and compared with the judgment of the sound in daily life. For example, the "rattle" sound caused by the dry friction of the bearing, and the "click" sound similar to the small hammer hitting the cement floor caused by the excessive valve clearance.

1. Correctly distinguish between normal and abnormal sounds.

The vibration of each mechanism in the work of the car will emit a variety of sounds, but the sound does not mean that the car is faulty, in order to avoid unnecessary disassembly, we must first distinguish between normal sound and abnormal noise. The normal vibration sound of each system component (such as the noise on the surface of the engine), the impact sound of the gear when shifting, the air intake sound and exhaust sound of using gas as the working source, and the gear meshing noise are all normal sounds. Abnormal noise (abnormal noise) can be divided into slight noise, general noise and malignant noise according to the impact on the performance of the car.

Slight noise, such as the flashover sound of high-voltage electric leakage, the slight loose sound of rolling bearings, etc., the general volume is small, the degree of wear of the parts is not large, and there is no significant change for a long time, and this kind of fault can still maintain the normal operation of the car without repair.

3. When diagnosing abnormal noise, attention should be paid to creating good auscultation conditions and trying to eliminate the interference of other noises, so as not to affect the accuracy of judgment.

It is best to consciously amplify the sound or reduce the Zen key, that is, use a screw or other metal rod as a stestological instrument to contact the sound part to amplify the sound of the group, or use a single cylinder fire cut-off method to reduce the sound to meet the needs of diagnosis. The auscultation site should be kept quiet to minimize human interference.

Yesterday the car just finished maintenance, but there was a big noise in waiting for the traffic light to hang the forward gear, the n gear was gone immediately, and there was a sound on the bumpy road, which rider knew what was going on yesterday The car was just maintained, but there was a big noise in waiting for the traffic light to hang the forward gear, the n gear was gone immediately, and there was a sound on the bumpy road, which rider knew what was going on The automatic transmission has an abnormal sound, and there are many traces, it is not the internal valve body that is damaged, but the stubborn dirt and impurities inside, In particular, the dirt and impurities inside the valve body accumulate to form a blockage, resulting in the inability to effectively adjust the oil pressure, resulting in the occurrence of frustration and impact and gear slippage. At the same time, the problem of high temperature of the gearbox cannot be ignored. According to the Automatic Transmission Repair Association, it is called

More than 90% of all faulty automatic transmissions are caused by overheating. "High temperatures can damage the quality and friction characteristics of the automatic transmission fluid, increase friction and wear, and transmission noise will follow, as well as sludge (impurities or dirt) can be generated inside the transmission (e.g. valve body), causing the transmission to stun and shock. If the temperature exceeds 120 °C, the rubber sealing material will begin to harden, eventually leading to leakage and reduced hydraulics.

If the temperature is higher, the gearbox starts to slip, which in turn causes the temperature to rise even higher. (Audi and other high-end models will call the police and enter the transmission protection mode) If it is not solved in time, the transmission will be scrapped. Therefore, only by removing the stubborn dirt and impurities in the gearbox and effectively controlling the working temperature of the gearbox can the gearbox problem be completely solved and prevent its recurrence.

As for your situation, it is likely that the viscosity of the engine oil is relatively large, or the oil is added more. If this is the case, it is recommended to observe after a period of time, as some oils will lose viscosity after a period of use. If it is caused by adding too much oil, you can go back to the 4S shop and ask the master to let it go (or take it out).

The car engine has abnormal noise and needs to be maintained.

There was a noise in the car. There is a cold car"When, when, when"The sound is likely to be an abnormal sound of the piston knocking on the cylinder. The so-called piston knocking cylinder abnormal sound refers to the abnormal sound caused by the piston side slapping the cylinder wall.

The decisive factor for whether the piston knocks the cylinder or not is the gap between the piston and the cylinder wall, and when the piston clearance is too large, the cylinder knocking is easy to occur. As the engine temperature rises, the piston clearance decreases and the cylinder knocking sound decreases.

There is a sound when the hot car climbs the hill, the engine is basically normal when the car is cold, and there is a sound when the hot car and heavy car accelerate, and this fault is a sound caused by the deflagration phenomenon. If the fuel label is too low, it is easy to deflagrate.

There was a dull rattle in the lower part of the engine. If the lower part of the body is muffled and becomes louder with the increase of engine speed, the transition sound from medium speed to high speed is the most obvious, and it is aggravated with the increase of engine load, which may be the abnormal sound of crankshaft bearing (large watts) or connecting rod bearing (small watts).

If it's a metal knocking sound, most of it needs to be repaired. If it is the sound of friction, it is not necessarily internal, and many cases are concentrated in the front of the engine where the pulley is installed.

You see you're up to the maintenance interval. The general car is 5000 kilometers or half a year, the first arrival shall prevail. Some cars are 7500 km.

Look at your car's service intervals. Under normal circumstances, if the car has not reached the maintenance interval, there will be no problem with the engine oil. Even if the maintenance interval is exceeded, if it is not too long, this problem should not occur.

There are not many cases of abnormal engine noises caused by engine oil. It is recommended to go to the SSSS shop to check it out. If the warranty period is not exceeded, then there is a problem that can be repaired for you free of charge.

If the engine has an abnormal noise, you dare to drive it, it is best to go to the maintenance department to find out the reason first! I don't think it's just a matter of maintenance.

There are many reasons that can cause abnormal engine noise, and oil decline is just one of them.

You can first use the oil drip ring test method to determine whether the oil has aged. Drop a drop of oil from the dipstick on the qualitative filter paper, stand horizontally for 24 hours, check the diffusion of oil droplets, if the central deposition spot is very black, and the outer ring diffusion ring is jagged, it means that the oil has been aged, and the oil and filter need to be replaced.

If the oil is not aging, other parts such as the feet should be inspected.

The engine judges the abnormal sound by the sound**, which is usually a metal screeching sound or a howling sound, and the following is a judgment about the abnormal noise.

1. The rubber of the machine foot is aging or loose.

The foot glue is the rubber block between the engine and the frame. Its function is to reduce the vibration and cushioning of the engine when working, and to have the effect of fixing the engine. Once these feet are aged or loosened, the engine will shake, resulting in abnormal noise.

2. The engine lacks cylinders and sells quickly.

Engine cylinder lack mainly refers to the engine has one or more cylinders are not working normally, which is generally manifested as: the exhaust gas flow from the car wheel has obvious intermittent conditions, and the exhaust pipe shakes badly, and the engine can be heard clearly"Sudden protrusions"Or a plop, plop sound. This phenomenon has a lot to do with the failure of the ignition coil.

3. "Knocking on the cylinder" abnormal sound.

Due to poor lubrication conditions, excessive wear of the piston and cylinder wall, resulting in the gap fit tolerance between the piston and the cylinder wall exceeding the normal range, the piston skirt and the cylinder wall collide when the engine is running, resulting in a crisp sound of "bell", which is generally more obvious when running at idle speed or low speed.

4. The mixture is too thick.

When the engine mixture is too thick, the phenomenon is: the engine is not easy to start; After starting, acceleration is difficult, the engine runs unevenly; black smoke from the exhaust pipe, the engine is accompanied by a "sudden" abnormal sound, and sometimes a cannon is fired; Engine power decreases, fuel consumption increases. This is mostly related to carbon deposits, filter blockages, etc.

5. Abnormal sound of timing gear.

After long-term use of gears, coupled with improper gear gap adjustment, gear belt hardening and other reasons, excessive wear will occur, and even the gear teeth will be worn bald in serious cases, and the meshing between the gears will be loose, and the machine will make a "bang, bang" sound when the machine is running.