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Thread: Air Escaping gas tank when I fill up

  1. #1
    Join Date
    Mar 2005
    Location
    Houston
    Posts
    26

    Default Air Escaping gas tank when I fill up

    Hi all,
    I've got an odd situation, apparently, every that I go to fill up with gas, I hear a small hissing sound when I insert the nozzle into the gas tank. It happens in cold and in warm weather, I'm just worried that it'll effect the MPG or some other problem with the car itself.

    Any ideas on what this is? Thanks!

  2. #2
    Join Date
    Dec 2003
    Posts
    571

    Default

    When the gas goes into the tank, the air gets displaced and comes out through the filler hole. Y'know, like when you jump in the bath and the water comes out...

  3. #3
    Join Date
    Dec 2003
    Location
    Eastern Tennessee USi
    Posts
    14,839

    Default

    lmao@dan
    95 E34 530I V2.37
    ===========
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  4. #4
    Join Date
    Mar 2005
    Location
    Houston
    Posts
    26

    Default

    I understand that, but it's just started to happen about 20,000 miles ago. Is this normal on a car that's over 100,000 miles?

  5. #5
    Join Date
    May 2004
    Location
    Japan
    Posts
    9,250

    Default

    Is it actually hissing when you open the fuel tank lid?
    If so, then check your fuel tank airation system.
    I know that the E38 had big problems with this and the vacuum became so big inside the tank, that the fuel tanks cracked.
    Many had to exchange the tanks and had to install a modified airation system.
    Sometimes this also can effect a bad warm start after a llonger drive. For example when you start with a full tank, then fuel level gets lower and vacuum increases and when you then try to restart the engine, the engine has to revv a long time still it runs.

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