dole2000 Posted August 8, 2005 Share Posted August 8, 2005 when I remove my cas cap to refuel my car makes a loud hissing or sucking noise like there is a vapor lock or something and the air pressure builds up and is only released when I remove the cap. It has gotten fairly dramtic. I think this is a bad omen as I need to get my car smogged in CA and this means something isn't right. Bob Quote Link to comment Share on other sites More sharing options...
SKperformance Posted August 8, 2005 Share Posted August 8, 2005 Buy a new gas cap if it is more than it normally is on other car you own. Quote Link to comment Share on other sites More sharing options...
SRK Posted August 8, 2005 Share Posted August 8, 2005 It is completely normal. Modern filler caps seal tight to the filler neck, and the engine manifold vacuum partially evacuates the tank to prevent HC vapour loss to the atmosphere. If the cap fails to achieve a seal, the PCM will normally set a code to indicate air entering the tank and the inability to achieve the partial vacuum. It is a part of the evaporative emission system. Quote Link to comment Share on other sites More sharing options...
larryp Posted August 8, 2005 Share Posted August 8, 2005 You may have a bad vapor cannister. Pressure got so high in mine that it pushed the wall of the gas tank out and caused a leak. Some hissing is normal, but if it feels like the cap is going to "blow off" when you unscrew it, then you probably have the same problem i had. In the 91 there is no check for loose gas cap as there is in newer LS's - leaving the cap off will not set the check engine light in the 91. You can try leaving the cap not fully sealed (don't let it click when turning) until you can have it checked out. Might also want to remove the cover in the trunk and look at the gas tank to see if it has "bumped out" anywhere. Mine looked like someone had taken a hammer and hit it from the inside of the tank. Quote Link to comment Share on other sites More sharing options...
dole2000 Posted August 9, 2005 Author Share Posted August 9, 2005 where is the vapor cannister located? I looked around under the hood and didn't find. Just asking this question makes me feel like a knobl Quote Link to comment Share on other sites More sharing options...
SKperformance Posted August 9, 2005 Share Posted August 9, 2005 Don't worry some questions are not that easy. I have no clue where my charcoal canister is ,but i have only had my LS for a couple of weeks and still have not done an oil change to take a good look in the nooks and crannies yet. Quote Link to comment Share on other sites More sharing options...
larryp Posted August 9, 2005 Share Posted August 9, 2005 It is located on the driver's side of the engine. It has 2 tubes going in the top and one coming out the bottom. There is a line that runs from the top of the engine to the charcoal cannister. The manual shows a procedure for testing that involves blowing compressed air through the cannister to check for blockage. An independant Lexus mechanic diagnosed mine so i haven't done the procedure myself. If the symptoms sound similar to what i described, i would strongly suggest you inspect the gas tank for "bulges". Quote Link to comment Share on other sites More sharing options...
akewlguy Posted August 9, 2005 Share Posted August 9, 2005 My car makes noise when I fill gas tank also. Heat or summer temperatures turns liquid into gas, while increasing pressure. This I suspect is a venting sound when you open gas tank. Not a big deal as far as I am concerned. Quote Link to comment Share on other sites More sharing options...
nc211 Posted August 9, 2005 Share Posted August 9, 2005 My 95 does this too, but primarily when the tank is below a quarter of a tank. You take the cap off, and it sucks in air, to balance out the pressure. I've had several other cars that did this as well "subaru outback, nissan sentra se-r and nissan maxima". I've never thought twice about it. Quote Link to comment Share on other sites More sharing options...
nc211 Posted August 9, 2005 Share Posted August 9, 2005 Opps, forgot the acura legend. Quote Link to comment Share on other sites More sharing options...
dole2000 Posted August 19, 2005 Author Share Posted August 19, 2005 seems the cooler weather as of late has more influence that anything else. It was like 100 degrees everyday for almost a month. That was a big part of the problem. Quote Link to comment Share on other sites More sharing options...
Lexls Posted August 19, 2005 Share Posted August 19, 2005 Try buying a new fuel cap gasket. You're supposed to replace it every once in a while. It has a notch in it...maybe that helps relieve pressure. Anyway, I replaced my gasket a while ago and on the next fill up there wasn't nearly as much of a pressure build up. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted August 28, 2005 Share Posted August 28, 2005 I thought they do not have gaskets to relive pressure anymore only valves so you don;t add gas vapour to the atmosphere unnecessarily Quote Link to comment Share on other sites More sharing options...
akewlguy Posted August 29, 2005 Share Posted August 29, 2005 I love the smell of the gas, so I will keep my old cap! AHHHH today my car will sit in Airport parking for 4 days. STINKS! Last time it was so dirty!! I have been using the polishes, waxes and glazes and the LEX looks awesome! Everyone now thinks it is a 2001. :) Yeah I am moving up daily! Cheers to you and LEXUS Quote Link to comment Share on other sites More sharing options...
Lexls Posted August 29, 2005 Share Posted August 29, 2005 I thought they do not have gaskets to relive pressure anymore only valves so you don;t add gas vapour to the atmosphere unnecessarily ← Well, my 1st gen does have a gasket ;). Maybe the 2nd and 3rd gens don't...haven't checked. Quote Link to comment Share on other sites More sharing options...
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