As the temperature rises, the gasoline inside your tank expands. Since the tank is relatively rigid, this expansion has nowhere to go, building up pressure. The popping sound you hear is likely the result of this pressure being released – either through a pressure relief valve (which is designed to do this) or through minor leaks or flexible seals which are stretched to their limit and give slightly.
Several factors can make this more pronounced:
* High ambient temperatures: The hotter it is, the more the gasoline expands.
* A nearly full tank: A full tank leaves less room for expansion.
* Age and condition of the fuel system: Worn-out seals or a failing pressure relief valve can make the popping more noticeable or even lead to leaks (which is a safety hazard requiring immediate attention).
* Direct sunlight: The gas tank being directly exposed to the sun's heat will exacerbate the expansion.
What you should do:
* Don't panic (unless accompanied by other symptoms). The popping itself isn't usually a sign of a major problem, especially if it's infrequent and a soft pop.
* Avoid filling your tank completely. Leaving some space allows for expansion. Fill it to about ¾ full, especially on hot days.
* Park in the shade when possible. This will reduce the amount of heat the gas tank absorbs.
* Listen for the sound's nature. If the popping becomes loud, frequent, or accompanied by other noises (hissing, gurgling), or if you smell gasoline, it's crucial to have a mechanic inspect your fuel system immediately as there might be a leak.
If the popping is concerning you, a mechanic can inspect your fuel system to ensure the pressure relief valve is functioning correctly and there are no leaks. Ignoring a potential fuel leak is very dangerous.
