What is the reason for the abnormal noise at the bottom after parking and turning off the engine?

After parking and turning off the engine, some people may hear a crackling sound from the bottom of the car. Some cars make quite loud noises, which are particularly noticeable in summer. Generally, the noise returns to normal after three to five minutes. Some people even go to the 4S store for inspection. Is this a problem with the car? This is not a problem with the car, it's the sound coming from the exhaust pipe. After driving for a long time, the temperature of the exhaust pipe will be very high, and the front part can reach 70-80 degrees Celsius. At this time, the exhaust pipe is in an expanded state. After parking and turning off the engine, the exhaust pipe is no longer heated and begins to cool down, in a state of heat dissipation. At this time, the metal in the exhaust pipe will contract and make a sound, so this sound is a metal contraction sound, which is normal. Don't run another trip to check it for nothing. Some people have heard this sound before, while others have not. It usually only appears after driving for a long time, and it is not easy to stop after driving three to five kilometers because the exhaust pipe is not very hot and has not expanded too much, so it will not shrink and make a noise. Therefore, it is not always heard after turning off the engine.

Some turbocharged cars have a delayed cooling function, and even after turning off the engine, the sound of the fan rotating can be heard, which is also normal. This function is specially designed to protect the turbocharger. In addition, when the engine is turned off, there will be no other sound. As long as the engine is turned off, all electrical equipment will stop working because if there is a power outage, all mechanical components will definitely stop working. Even if a component is damaged, there will be no sound. So, the sound that occurs after parking is generally normal and does not require inspection or repair. If abnormal sounds are heard while driving, they need to be checked in a timely manner.

Similarly, there is water dripping from the exhaust pipe, which is not a fault. Some people see severe dripping in the exhaust pipe, thinking that it is a leaking part of the car, and they also take it to the 4S store for inspection. In fact, this is a normal phenomenon and does not need to be checked. The most abundant products produced by complete combustion of gasoline are carbon dioxide and water. Generally, water is discharged in the form of water vapor, and we cannot see it unless it condenses into small water droplets. What we usually see is that when water vapor reaches the end of the exhaust pipe, due to the low temperature of the exhaust pipe, it will condense into small water droplets and adhere to the wall of the exhaust pipe, accumulating more and eventually forming water flowing out.

If it can be determined that the liquid on the ground is flowing out of the exhaust pipe, no inspection is needed because even if there are other liquid leaks on the car, they will not flow into the exhaust pipe and then out of the exhaust pipe. If you see liquid on the ground while driving and don't know where it leaked out, move the car to see if it's oil or water. If it's water, it's normal. If it's oil, further inspection is needed. There is liquid on the ground. If it is in the middle of the rear of the vehicle, it is usually water in the exhaust pipe. If it is at the bottom of the engine, it may be oil leakage. If the air conditioning has been driven, it may also be air conditioning water.

From: WONDEE Autoparts

2024-6-3