New freightliner cascadia air compressor continues running

Discussion in 'Experienced Truckers' Advice' started by American trucking, May 21, 2022.

  1. American trucking

    American trucking Bobtail Member

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    May 21, 2022
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    Hii i just bought new freightliner cascadia from first day I noticed the air dryer purge every minute sometime 30 sec and sometime every 2 minute. I took truck to dealership they changed the air dryer but it still doing same and the dealership said this is normal. Keep driving. So now I noticed that first the air dryer purge (a small noice of shi shi) then it start the air compressor for 10 to 15 sec then again air dyer purge and then after 1 min air dryer purge again and start the air compressor again and this continues on idiling as well as road . And the air pressure of primary and secondary always stays on 123 to 125 psi
     
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  3. supersnackbar

    supersnackbar Road Train Member

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    Defective or improperly installed air governor most likely.
     
  4. American trucking

    American trucking Bobtail Member

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  5. AModelCat

    AModelCat Road Train Member

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    Leak somewhere between the compressor and wet tank or in the governor/unloader circuit.
     
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  6. Studebaker Hawk

    Studebaker Hawk Road Train Member

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    The primary air pressure gauge should show a decline in air pressure.
    It will get a signal from the air governor to cut in the compressor. (100 psi or so )
    The air pressure should go up to cut out pressure ( 125 psi or so, sometimes higher)
    The air dryer will cycle ( pfffsssttt)
    And it begins all over again.
    Under normal circumstances in a new truck going down the road or sitting still it shouldn't happen more than every 15 minutes.
    How much pressure do you lose when the truck is just sitting everything off? If memory serves it should be less than 2 psi per minute.

    Check for air leaks throughout the system.
     
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  7. supersnackbar

    supersnackbar Road Train Member

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    Thought they just changed the dryer
     
  8. American trucking

    American trucking Bobtail Member

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    Truck only loss 5 to 10 psi maximum for sitting one day or more
     
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  9. American trucking

    American trucking Bobtail Member

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    The air drye
    and they changed air. Governor too
     
  10. Dave1837

    Dave1837 Road Train Member

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    Sounds like an unloader valve in the compressor. The Mack I drive did the same exact thing. Is it a brand new truck? Or a new used truck
     
  11. AModelCat

    AModelCat Road Train Member

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    Truck should have 3 tanks. Air compressor should pump air into the wet tank. From there the air will be distributed into the primary and secondary air tanks. Air should not backflow from the primary and secondary into the wet tank as they're protected by check valves. If there's a leak between the compressor and wet tank or a leak between the governor and wet tank you will not see it reflected on the pressure gauges.
     
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