does it mean there is way too much pressure in there?
do you get better mileage when it doesnt do the "whoosh"
what exactly does it mean when you hear that sound?

 

It means your gas tank is pressurized correctly. The woosh you hear is just the gas tank de-pressurizing, that is, matching the gas tank pressure to the ambient air pressure.

 

yep what he said.

 

i see on lexls says that if you hear that, you need to replace the gasket, or cap itself.

my owners manual also said i need to replace it every so often too so i just wondered what it meant when i heard that (other than I need to replace the gas cap)

 

not true, it means just the opposite, ur cap is working correctly

 

but when i first got the car the cap never did that, but now it does for the past 2 months or so the "whoosh" has gotten stronger, so i thought that was a sign of needing to replace it.

so what are the actual symptoms of needing to replace the cap?

 

no ill bet when the noise is more previlant ur tank is almost empty

 

i think it's just really thirsty...

 

At least, that's the way it should work.

 

yeeah, if you normally refill the tank before it hits say the 1/4 tank mark, you pulll less internal pressure than if you run it til nearly empty.

 

it actually made that whoosh yesterday while i was at just below 3/4ths

 

its just ur gas tank being depressurized. in most jobs requiring you to do anything with fuel, it tells u to depressurize the tank by unscrewing the gas tank cover first.

 

okay good info to know,

so can anyone answer WHY exactly do we need to replace the cap?

 

sometimes the gasket deteriorates over time and will need replacing..

 

Since you hear the whoosh it means your cap is good as the gasket is keeping the pressure in.