Mistery sound.

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Patilan, Aug 14, 2022.

  1. Patilan

    Patilan Bobtail Member

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    Mar 17, 2013
    0
    Hi all,
    I just did a rebuild on my engine Cummins N14 Celect Plus, in a '99 Century.
    I started getting that weird high pitch sound, when I get up to 10th-11th gear (13 speed) around 1500rpm, the sound stays on for a few seconds, then it goes away on its own. No other changes in the truck going down the road, no vibrations, loss of power, or oil pressure change. I have pulled only empty trailer with it, so don't know if the power is OK when loaded. I took my mechanic for a ride and he seems confused too, doesn't know whee it might be coming from.
    Can anyone recognize the origin of this sound, where it may be coming from? I made a video of it, you have to turn on the volume, the sound starts about 5-6 seconds into the clip, then stops, then appears again around 20 seconds.
    https://www.youtube.com/shorts/65_cJBqqKwY
     
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  3. Heavyd

    Heavyd Road Train Member

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    Boost or exhaust leak. Check your air to air clamps, exhaust manifold and turbo flange gaskets for leaks.
     
  4. Patilan

    Patilan Bobtail Member

    29
    5
    Mar 17, 2013
    0
    Thanks for your response. That's what I thought as well, but if it's a boost or exhaust leak, wouldn't the whistling going to be present most of the time and stay on for longer, almost all the time when I am driving in higher gear? That thing stays on for just a few seconds and then goes away.
     
  5. God prefers Diesels

    God prefers Diesels Road Train Member

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    No. I've had exhaust leaks twice (both times my own fault). I can pin the throttle, and it will make noise, and then kind of peter out. If the noise has some lag to it, then you've probably got a boost leak. If you can make it almost immediately come on with throttle, then probably an exhaust leak. The fact that the noise kind of "goes away on it's own", plus you just did a rebuild makes me lean towards exhaust. A boost leak almost sounds kind of nice if you like that sound to begin with. An exhaust leak will make you want to kill yourself after about five minutes.
     
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  6. AModelCat

    AModelCat Road Train Member

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    Just had a 6.7L Cummins make an identical noise when exhaust braking. Leaking exhaust manifold.
     
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