Forum Discussion

beany's avatar
beany
Explorer
Dec 18, 2013

Vacuum leak on gas Allegro??

Hi Folk....
We have a 2005 Allegro on a workhorse platform and have noticed a hissing sound coming from the rear of the RV. Seems to be a constant vacuum leak or air pressure leak sound but everything works fine and could find no source while snooping around underneath. Its a gas rig so shouldn't be any vacuum lines or air pressure.
Any thoughts on what it might be and should I be worried ???
As Always.. Thanks Guys
Don Ashley
Class A
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Dec 18, 2013
    If it only happens when the engine is running it could be from the fuel cap that is making noise as air is sucked in to replace the fuel being used. A new fuel cap may eliminate the noise.
  • Argosy24's avatar
    Argosy24
    Explorer
    Dec 18, 2013
    rgatijnet1 wrote:
    If it only happens when the engine is running it could be from the fuel cap that is making noise as air is sucked in to replace the fuel being used. A new fuel cap may eliminate the noise.


    The caps are sealed now as part of emissions, air to replace fuel used comes through the carbon canister.
  • wolfe10's avatar
    wolfe10
    Explorer
    Dec 18, 2013
    Don,

    Not aware of any vacuum or pressure line in the back of a gas coach. Do you have supplemental rear air bags???
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Dec 18, 2013
    Argosy24 wrote:
    rgatijnet1 wrote:
    If it only happens when the engine is running it could be from the fuel cap that is making noise as air is sucked in to replace the fuel being used. A new fuel cap may eliminate the noise.


    The caps are sealed now as part of emissions, air to replace fuel used comes through the carbon canister.


    That is exactly right, but suppose the seal is not good on the fuel cap. I assume this is something that has not been going on since the coach was new so it may be possible that the seal could have cracked or split on the fuel cap.
  • beany's avatar
    beany
    Explorer
    Dec 19, 2013
    wolfe10 wrote:
    Don,

    Not aware of any vacuum or pressure line in the back of a gas coach. Do you have supplemental rear air bags???


    No , no air bags. It sounded loudest center of fuel tank , at least from under neath. Maybe a intank fuel pump pooping out ???
  • wildmanbaker's avatar
    wildmanbaker
    Explorer
    Dec 19, 2013
    Don,

    You may have found a problem in the developing. Usually, if an in tank fuel pump starts making noise, it is on a short course to failure, and usually in hotter weather.

    Good luck
  • wildmanbaker's avatar
    wildmanbaker
    Explorer
    Dec 19, 2013
    Don,

    You may have found a problem in the developing. Usually, if an in tank fuel pump starts making noise, it is on a short course to failure, and usually in hotter weather.

    Good luck

About Motorhome Group

38,705 PostsLatest Activity: Jan 14, 2025