Why does the engine still buzz after the car is turned off?
3 Answers
The reasons why the engine still makes noise after the car is turned off are as follows: 1. Electric fan operation: When the engine temperature is too high, even if the car is turned off and the key is removed, the cooling system will automatically activate to cool down the engine system, resulting in the buzzing sound, which is caused by the high-speed rotation of the electric fan. 2. Engine temperature decrease: After the engine system temperature drops, the cooling system will automatically stop working. This situation usually lasts for three to five minutes. Besides the engine, some other electronic devices may also exhibit similar behavior. For example, in some high-end cars equipped with a sunroof ventilation system, the sunroof exhaust system may continue to operate for ten to twenty minutes after the car is turned off to expel excessively cold or hot air from the cabin, ensuring the temperature inside matches the outside.
I've encountered the situation where the car keeps buzzing after turning off the engine several times. At first, I thought the engine hadn't completely shut down, but later when I asked a friend to take a look, I learned that most of the time it's the cooling fan continuing to operate. After the engine is turned off, if the temperature remains high, the fan will automatically run for a few minutes to cool down, which is particularly common in hot weather or after a long drive. However, if the noise persists for more than five minutes or sounds unusually harsh, there might be a minor issue, such as a stuck fan relay or loose wiring. In such cases, it's best not to ignore it, as it could affect the battery's charge—for example, the fan running continuously could drain the battery, making it difficult to start the car next time. My suggestion is to wait a few minutes after turning off the engine. If the noise continues, open the hood and briefly check if the fan is stuck. If the problem persists, it's best to take it to a repair shop for a professional inspection to prevent a small issue from turning into a bigger one.
If the car keeps buzzing after turning off, it's likely the cooling fan hasn't stopped. I've experienced this several times with my own car, especially after driving in summer - the fan often continues running for anywhere between dozens of seconds to two minutes. This is a normal cooling design to prevent heat damage to components. However, if the sound persists abnormally (e.g., lasting over three minutes) or fluctuates in volume, there might be an issue: common causes include aging fan motors, short circuits, or relay failures. The DIY checks are quite simple - after turning off the engine, observe the fan's position and feel if the blades are excessively hot or vibrating too much; if they rotate freely, it's working fine. Remember not to directly disconnect the battery cable, as this might damage the system. Neglecting such minor issues can waste fuel or battery power, so early troubleshooting saves both hassle and money.
