Trailer making high pitched noise

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ach1998, Apr 8, 2021.

  1. ach1998

    ach1998 Bobtail Member

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    Apr 8, 2021
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    Hearing a high pitched timing/whistling noise coming from trailer, specifically around the air tank area, anyone know what might cause this? I found a air bag with a very minuscule leak that I’m getting changed out tomorrow, hopefully that gets rid of it, but every time I release the trailer brakes, the noise comes back as it’s filling the tank. The hoses have also been changed out recently.
     
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  3. John E Walker

    John E Walker Light Load Member

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    That noise happens when you release the brakes?

    It's a sign of the high pressure valve opening. Study how the service brakes work you might find which valve is potentially failing or needs lubrication. It's similar to blowing a trumpet horn and the higher pitch is caused by the opening of the mouthpiece controlled by pursing the lips and air pressure from exhaling.
     
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  4. ach1998

    ach1998 Bobtail Member

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    Apr 8, 2021
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    Yes when I release the trailer brakes. And yes that’s an exact comparison to what it sounds like.
     
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  5. John E Walker

    John E Walker Light Load Member

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    There is a possibility moisture has built up in the air system, Even though it is a closed system, the compressor must draw from the outside ambient environment. There is a dryer for the Service on the Air-Supply that sometimes needs checking. They also sell a drying agent ( alcohol based to evaporate the moisture.) During winter that moisture can freeze and cause the brakes to fail on trailers. I would suggest having the service department at your shop look at it to determine a quick fix.
     
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