Where does the small hole next to the fuel tank cap lead to?

[AngelinaFitz]

The small hole next to the fuel tank cap leads to the interior of the fuel tank to balance the internal air pressure. Here are the relevant explanations: 1. Function: A completely sealed fuel tank would create a vacuum as the fuel level gradually decreases, leading to insufficient fuel supply or failure to supply fuel normally. The evaporation of high-temperature fuel would increase the internal pressure of the tank, causing excessive fuel supply or directly forcing fuel into the crankshaft case. Therefore, a small vent hole is often provided on the fuel tank cap to balance the internal and external air pressure. 2. Consequences of blockage: If the small hole is blocked, it will result in insufficient exhaust of the fuel tank, making it difficult to fill the tank completely when refueling. In severe cases, it may even lead to fuel leakage from the tank.

[Archer]

Having driven for many years, I often pay attention to the small hole near the fuel tank cap. It may seem insignificant, but it plays a crucial role—mainly for drainage. This small hole is designed into cars to allow water or liquids, such as rainwater or car wash water, to flow out, preventing accumulation around the fuel tank cap. These small holes lead directly to a small outlet beneath the car, not connected to the fuel tank interior or other sensitive components. Otherwise, accumulated water can cause rust, corrosion, and even damage the car paint. I once experienced this after a car wash when I neglected to clean it—the hole got clogged, and water accumulated near the fuel tank cap for several days, causing the metal parts to rust. I regretted it deeply. Remember to regularly check this small hole; you can use compressed air to blow it out or a small tool to remove debris, keeping it clear. Especially during the rainy season or frequent car washes, prevention is key.

[MaxDella]

From a structural perspective of the vehicle, the small hole next to the fuel tank cap leads to an external drainage channel. In terms of design principle, it is a small aperture—simple yet efficient—preventing the accumulation of rainwater or dust, directly connecting to the drainage outlet at the vehicle's chassis. If drainage is obstructed, trapped liquids can erode the car body, accelerating corrosion or causing electrical component issues. Based on experience, a common problem is blockage by leaves or mud, leading to water backflow into the fuel tank area. Cleaning it with a soft wire is usually sufficient. Don’t overlook this detail; though small, it plays a vital role in maintaining the vehicle's overall health, especially in high-humidity regions where improper maintenance can increase repair costs.

[ValeriaDella]

I think this small hole is quite important as it serves to drain water and liquids. When refueling, I often notice it and wonder where it leads—it actually connects to the drainage path outside the car body. Its purpose is to allow water to flow out quickly, preventing corrosion of the metal around the fuel tank. Once, while washing the car, I didn’t notice the hole was blocked, and after a few days of water accumulation, I found rust spots around the fuel filler neck, which were troublesome to clean. I recommend everyone to periodically check if the hole is clear—simple maintenance can prevent major issues.