Hey guys, when I take the gas cap off should I hear a noticable hiss from the pressure in the gas tank? This struck me as odd one day when I had to take off the gas cap to relieve pressure, but I didn't notice any release. Every other car I have makes a loud hissing sound when the cap is removed. Could this be the result of a faulty cap? Thanks.

oh btw it's one of those locking gas caps, it came with the car.

 

Damn it, I guess no one looks in this forum much. Do you guys notice pressure coming out when you take off your cap to fill up or what not?

 

If you aren't hearing any pressure release hiss when you open it, it probably means your cap isn't sealing fully - either it wasn't tightened enough when you closed it, or the cap is defective/damaged. I'm no expert though

 

Never hear a hiss noise, I click it hella times too when I close it. Weird, but if it isn't throwing any codes, then it should be cool.

 

It usually only happens when you run the tank down to almost nothing and the vapors are almost the only thing in the tank.

 

Heh, think this might be the reason it doesn't do it on these cars but does it on so many others... the evap system! doh. "The emission control system that prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine." So that would keep the vapors from building up in the tank in the first place. I should've thought about it more instead of assuming it was the same for all types of cars