Funny sound shortly after takeoff

Discussion in 'Prime Main Forum (2017-Current)' started by ppongi, Sep 2, 2017.

  1. bisco

    bisco cookie crumbler

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    hang on, your gas cap turns itself?:eek:
     
  2. bisco

    bisco cookie crumbler

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    too flat around here.
     
  3. scm2000

    scm2000 Active Member

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    The prime has a pressurized fuel system. You don't just pop the fuel door and open the cap. You press an electronic button that depressurizes the system and opens the fuel door. you open the cap.. fill with gas, put the cap back on and turn it slightly until it clicks... It then backs off the cap counter clockwise all by itself...

    It's in the manual and it was spooky the first time filling to see the cap move.

    Judging on where the sound seemed to be coming from I would bet that it has to do with preparing the fuel system for HV driving.
     
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  4. scm2000

    scm2000 Active Member

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    Just for reference... page 266
    "Closing the fuel tank cap

    After refueling, turn the fuel tank cap until you hear a click. Once the cap is released, it will turn slightly in the opposite direction.
    "

    The sound may be from it pressurizing the system and any cap adjustments.... Just a guess.
     
  5. bisco

    bisco cookie crumbler

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    wow, that is incredible!
     
  6. scm2000

    scm2000 Active Member

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    I've read up on it. Basically its to prevent evaporating fuel vapors escaping into the atmosphere. normal cars have charcoal canisters that catch the vapors... and return them to the tank when the engine runs.
    On cars like the Volt or Prime where the engine might not start for six months or a year... they'd either have to have giant canisters, or what they have which is a pressurized sealed fuel system.
    How desiging the Chevy Volt's sealed gas tank brought automakers, CARB together - Autoblog

    Still a guess though... I'm wondering if the original poster has an idea of where their sound is coming from....
     
  7. bisco

    bisco cookie crumbler

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    i would love to see the mechanism that turns the cap, and how it works.
     
  8. scm2000

    scm2000 Active Member

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    ah... ok...

    I just tried it again.. just opened the cap, and put it back on... it looks like the cap itself is spring loaded... so probably I'm wrong and it can't turn the cap at will..

    When I fueled it... I turned it to click and let go -- after a delay it moved the other way...

    This time without adding fuel it just seemed spring loaded... you click it clockwise, it springs back counter clockwise... but then again the car knows I didn't put gas in.

    next time I really put fuel in I'll video it.
     
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  9. bisco

    bisco cookie crumbler

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    i'm all eyes. my pip works the same way, but i don't think i've ever looked at the cap after it clicks, just shut the door and go.
     
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  10. ppongi

    ppongi Junior Member

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    One thing I am sure of is that chirp or clank sound is not auto-doorlock as the doors automatically lockup when it goes into D mode and not into driving about 100-200 yards. Further, it seems it has nothing to do with speed. Driving slow or fast, uphill or downhill I hear that chirp sound. So, you could be right about the pressuring gas tank. But, then I would guess everyone Prime owners probably heard that chirp sound. Maybe I am too sensitive.
     
  11. Son of Gloin

    Son of Gloin Active Member

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    No ideas here, but I think I heard what you're talking with mine for the first time just yesterday... it only lasted 2 or 3 seconds, and was NOT very obvious (if my wife had been with me, my guess is she wouldn't have noticed it)....
     
  12. Son of Gloin

    Son of Gloin Active Member

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    I think I heard it, too, but I was on a dead-level residential street and traveling at about 20-25 mph (steady speed)... this was within the same block where I live, so VERY soon after "take off". So I (personally) don't think MY particular situation was at all brake-related.
     
  13. scm2000

    scm2000 Active Member

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    ok heard it today in ev mode
     
  14. Mark57

    Mark57 Senior Member

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    Here it is. ;)

    [​IMG]
     
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  15. Dale Leonard

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    Ok let's try this theory. When cars are parked the tires get a flat spot. Then when you start out the tires could chirp before they go round. Traction control?

    Ok, might be a really dump idea.

    When it happened to me, I thought traction control.
     
  16. mdhare

    mdhare Member

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    Noticed it twice today. First, downhill at 15mph and was more like a clunk. Second time, relatively flat at about 13mph. In each case within a short distance like OP. I may try experimenting starting or really slow to see what happens. Again, to me seems like it is in engine compartment directly in front of driver, so mg1/mg2 territory.

    I don't think the sound is new, just observing it more as I am listening for it.
     
  17. mdhare

    mdhare Member

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    Stupid question time, any report of this on a gen4? A 60s Google search didn't find likely matches. I know someone who owns one, might take a while to get a report though. I know I keep speculating about traction motors but doesn't prime have a unique clutch for mg1? Just saying. :)
     
  18. ppongi

    ppongi Junior Member

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    Now I am like; what the heck? Dang it! evertytime I heat that chirping or clunky sound.

    It is what it is and time to move on. Hope it's not related to faulty design or defective workmanship though.
     
  19. bwilson4web

    bwilson4web i3 and Prime

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    I would have the motor mounts and front steering assembly inspected. Tell the service writer.

    Bob Wilson
     
  20. scm2000

    scm2000 Active Member

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    if you listen carefully the car makes a barely audible hmmmmmm sound about every 10 seconds.

    Step on the brakes it makes that familiar bzzzzdt sound.

    roll at low speeds it makes a slight wahweewahwee sound to warn pedestrians.

    Priuses make sounds. they are complicated cars with a lot of systems.
     
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