TeeJay3800 Posted August 9, 2005 Report Share Posted August 9, 2005 I have a weird problem with my gas tank. Every time I open the gas cap, whether its hot or cold, a TON of air pressure blows out. Its been doing this for quite a while, but it hasn't always. Is this a sign that something is wrong, or is it normal? Thanks guys. Any help is appreciated. Quote Link to comment Share on other sites More sharing options...
DiscoStudd Posted August 9, 2005 Report Share Posted August 9, 2005 Totally normal when it's hot outside. Try sticking a plastic gas can (half-full) inside your garage or shed when it's 80+ degrees outside. After a couple of hours in the heat, the gas can will be bulging at the seams... Quote Link to comment Share on other sites More sharing options...
Turbocharged400sbc Posted August 9, 2005 Report Share Posted August 9, 2005 This means your evap system is working perfectly to keep Hydrocarbons from escaping into the atmosphere... newer cars will run a vacume test and can detect a leak .002 inches in diameter, any car i come acrost with P0440 (large Evap leak-OBDII) I usually end up just tightening the gas cap all the way, and charge the customer 30$ for hooking up the scanner...normally its $50 but i feel bad for some peoples stupidity... after paying 30 dollers to find they didnt tighten the gas cap all the way they never seem to have it happen again... its good fer the environment Quote Link to comment Share on other sites More sharing options...
slick Posted August 9, 2005 Report Share Posted August 9, 2005 This means your evap system is working perfectly to keep Hydrocarbons from escaping into the atmosphere... newer cars will run a vacume test and can detect a leak .002 inches in diameter, any car i come acrost with P0440 (large Evap leak-OBDII) I usually end up just tightening the gas cap all the way, and charge the customer 30$ for hooking up the scanner...normally its $50 but i feel bad for some peoples stupidity... after paying 30 dollers to find they didnt tighten the gas cap all the way they never seem to have it happen again... its good fer the environment Sad thing is, I'd do the exact same thing. Quote Link to comment Share on other sites More sharing options...
Justin Posted August 10, 2005 Report Share Posted August 10, 2005 Sad thing is, I'd do the exact same thing. Sad thing is, I do do the exact same thing, just did it today in fact. I told her it needed a new cap though, the cust. doesn't ask as many questions that way. .6 hrs to clear the code and replace the cap. Quote Link to comment Share on other sites More sharing options...
TeeJay3800 Posted August 10, 2005 Author Report Share Posted August 10, 2005 I understand the concept of materials expanding with heat, but other cars I deal with don't do the same thing. I opened a friend's Lumina gas cap just after opening mine, and no compressed air escaped. Also, my car didn't use to do this whether it was hot or cold. What codes are you guys talking about and what was cause? Quote Link to comment Share on other sites More sharing options...
bartonmd Posted August 10, 2005 Report Share Posted August 10, 2005 I was thinking that they weren't supposed to do that... After all, the "air" that comes out when you open the cap is the same air/fuel vapor mix that the Evap system is put in place to get rid of... Mine does the same thing, but my dad's '93 Lumina doesn't, nor does my mom's '96 cutlass, or their '04 Impala... I don't think it's worth messing with, because we don't have emission testing or checks or anything around here, but I really think the evap system is clogged or just not working at all... Mike Quote Link to comment Share on other sites More sharing options...
1990lumina Posted August 11, 2005 Report Share Posted August 11, 2005 My Lumina does that as well...it was only mid 60s here yesterday when I filled up, and lots of pressure came out. I've never thought much of it...although my car is the only one in the family to do this....we don't have emissions testing, and I personally don't care/it hasn't worried me to much. Car still runs fine and whatnot... Quote Link to comment Share on other sites More sharing options...
turby Posted August 11, 2005 Report Share Posted August 11, 2005 Every car I've ever owned only had air build up when the tank was damn near empty. Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted August 11, 2005 Report Share Posted August 11, 2005 My GP did this all the time. My Bonneville does it every so often. I really wouldn't get too worked up over it. Quote Link to comment Share on other sites More sharing options...
Prospeeder Posted August 12, 2005 Report Share Posted August 12, 2005 isnt there like, a little vent system, so it doesnt build up vacuum when the gas gets sucked out? that would release pressure wouldnt it? or is it like a valve Quote Link to comment Share on other sites More sharing options...
Redwingvksm Posted August 12, 2005 Report Share Posted August 12, 2005 When I had the regal - and I let it get below 1/4 tank it'd actucally pull a vacuum. When you opened the gas cap you'd hear it suck... It's a W-Body thing... Quote Link to comment Share on other sites More sharing options...
pitzel Posted August 12, 2005 Report Share Posted August 12, 2005 Yup i burned 65L out of my 62L tank one night, and it sucked like a mofo for the first 10 seconds after the cap was pulled off. Quote Link to comment Share on other sites More sharing options...
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