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Q: Hissing noises coming from the gas tank area

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Recently, the van started making unusual hissing noises. I tried to pinpoint where it is coming from and it seems to be originating from the gas tank area. The noise lasts only for several seconds in intervals, which can last up to a couple of minutes. The noise is similar to air being released, or as if the water is running in the next room. It occurs after the van sat for a while and also when the weather is very cold. What could be the problem?

A: Hey there. From your description, it sounds...

Hey there. From your description, it sounds like you are hearing the Evaporative emissions system perform its routine checks. The computer will check the fuel tank and evaporative emissions hoses for leaks. If conditions are right, the pressure will build inside the tank during testing and the computer and may vent that pressure causing a hissing sound. Look to see if your Check Engine Light is on. That may indicate that there is a leak in the evaporative emissions system that is causing the hissing sound. If the light is not on, I wouldn’t worry much about the noise as I believe this is normal. If the noise seems to worsen in any way, or you begin to notice drivability concerns, have a local expert, like one from YourMechanic, diagnose the noise in order to determine what is going on.

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