Exhaust line leaks air on brake application.

Discussion in 'Volvo Forum' started by bowtieboy77, Nov 15, 2021.

  1. bowtieboy77

    bowtieboy77 Light Load Member

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    Aug 16, 2013
    Southern, Ontario
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    I have been working on a 2008 volvo vnl plow truck. Regardless if the park valve button is in or out if I make a brake application air will constantly leak out the yellow exhaust line under the cab that I believe runs to the park valve. The unit does have both Yello and red buttons but does not tow and the outlet ports of the tractor protection valve are plugged. I suspect something in the system is back feeding just do not know what. The park valve (dash valve) has been replaced and problem still exists.
     
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  3. nasriza

    nasriza Road Train Member

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    Feb 1, 2013
    Chicago, IL
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    if it has a johny bar that has seperate exhaust as well sometimes thats the culprit.
     
  4. bowtieboy77

    bowtieboy77 Light Load Member

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    Aug 16, 2013
    Southern, Ontario
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    Thanks Nasriza it does not have a spike but it turned out to be a faulty tractor protection valve. It is a plow that is the third spare and selling in spring that never has had a hitch or trailer cords so I eliminated the valve by plugging the supply lines.
     
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