Warm-Up Period Exhaust Noise?

Discussion in 'General Motoring' started by Don Allen, Jan 14, 2010.

  1. Don Allen

    Don Allen Guest

    I have a problem that's been getting worse for about the last 3 months
    with our 2006 Elantra GLS automatic with only 30K miles. When I drive
    off with a cold engine/tansmission, during the first several miles of
    city driving, and only when stopped at a light with the transmission
    in Drive and my foot on the brake, there's an apparent exhaust
    "knocking" sound emanating from forward of the gear selector. I've
    checked the exhaust system, and there doesn't seem to be any conflict
    with any chassis members beneath the car (my first thought). It's
    not an engine knock or piston slap, as I've already looked into this.

    During the period of the noise progressively getting worse, I've also
    noticed a change in the exhaust sound, especially on acceleration. It
    sounds a bit "blatty," if you will - excuse the poor word choice -
    almost like a muffler in the process of failing. But, this shouldn't
    cause the knocking sound, as I would think a loose internal baffle
    would create a knocking sound. The knocking sound could perhaps also
    be construed as a pronounced rattle. For those who live in the snow
    belt, the sound is very similar to an exhaust tip on the back of the
    car knocking against ice build-up.

    I've had a couple of thoughts, the first somewhat logical, and the
    second, out-of-the-box:

    1). The flex joint,

    2). The rear engine mount (mounted to the transmission I believe)???

    I had the 48K or 4 year service performed at the local Hyundai dealer
    in December. The noise was present prior to taking it in, but they
    didn't hear it as the engine/transmission was still warm when then
    drove it into the shop for the work. I have noticed that the curb
    idle speed is a bit lower than prior to the service, and this lower
    idle speed exacerbates the knocking noise.

    Any ideas?
     
    Don Allen, Jan 14, 2010
    #1
  2. Don Allen

    Don Allen Guest

    Quick edit to my post:

    "...as I would think a loose internal baffle would create a knocking
    sound."

    Should have read:

    "... as I would think a loose internal baffle wouldn't create a
    knocking sound."

    Sorry --

    Don
     
    Don Allen, Jan 14, 2010
    #2
  3. Don Allen

    Don Guest

    Hyundaitech or others, any input on this? I'm going to take another
    look tomorrow, and try to localize the source. I know what a bad flex
    joint sounds like on Dodge Caravan, but not on an Elantra, so I'm only
    guessing here.
     
    Don, Jan 16, 2010
    #3
  4. Don Allen

    Ed Guest

    I would almost say it sounds like the noise my 01 elantra makes when
    it's cold. But that is just the oil not reaching the top end yet, and
    that goes away within a 30 seconds. I would suggest leaving the car
    overnight with the dealer and tell them to leave it outside so it's nice
    and cold in the morning. That way they can hear it for themselves
    firsthand. Also you might try postin this over at www.elantraclub.com we
    have a few techs in the club that may be able to help.
     
    Ed, Jan 17, 2010
    #4
  5. Don Allen

    Don Guest

    Thanks Ed. I will give that a try, before taking the car into the
    dealer.
     
    Don, Jan 18, 2010
    #5
  6. Don Allen

    hyundaitech Guest

    Sorry about being late to the party here. The flex pipe and motor
    mounts are potential causes, as would be perhaps a cracked exhaust
    manifold.
     
    hyundaitech, Jan 24, 2010
    #6
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