Strange sounds coming from gas cap

Hi Everyone ! My name is John. I just bought a 2002 Toyota 4Runner limited with 102,000 miles on it. It is great shape and I love the vehicle. I have one question and I am hoping you experts can help. When I open the gas cap after driving the car for say 20min. there is a whooshing of air sound like the system has pulled a vacuum. Also if I don't open the gas cap I hear a burping sound coming from the gas fill area that stops after 30 mins. and the pressure has normalized. Is this normal. I have never experience that in any other vehicle. I am suspecting a venting issue / check valve issue. Any help would be much appreciated.

 

Since it's a pressurized system, you will hear air escape when you open gas cap. As for the burping sound, I haven't experienced it. I really don't think you have anything to worry about.

 

Thanks so much for your reply ! This is new to me so I was a little unsure if this was an issue.

 

Yeah, it should Whoosh. That is letting you know your evap system is ok. Unlike mine that never whooshes anymore and every 2 months throws an evap code. Modern cars have a very closed fueling system which tries to capture all vapors from being emitted into the atmosphere.

 

Thanks everyone...just got a new cap and all is good.