Is it normal to hear a gas sound when opening the fuel tank cap?
2 Answers
It is not normal and is caused by a difference in pressure inside and outside the fuel tank. When the internal pressure of the fuel tank is lower than the external pressure, the following situations may occur: 1. Due to the internal pressure being lower than the external pressure, the fuel tank is prone to deformation and damage. 2. Because the internal pressure is lower than the external pressure and the tank is not vented, the fuel pump will draw outward, potentially damaging the pump. 3. During summer, high temperatures cause gasoline to expand. Since the fuel tank's volume is fixed, the vaporized gasoline creates pressure. When the internal pressure exceeds the external pressure, opening the fuel tank cap will release the gasoline vapor, resulting in a "gas release sound."
It's actually quite common to hear a hissing sound when opening the fuel tank cap, especially in summer or after a long drive. This happens because gasoline evaporates and creates vapor, building up pressure inside the tank. When you unscrew the cap, the sudden release of this pressure produces the 'hiss' sound. I used to find it alarming too, until an experienced mechanic explained that it's normal. However, if the sound is unusually loud and accompanied by a strong gasoline smell, you should be cautious. This could indicate a clogged charcoal canister or an issue with the vent hole in the fuel cap. In such cases, it's best to have it checked at a repair shop to prevent fuel vapors from accumulating in the vehicle, which poses safety risks.
