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air pressure problem need help, 2004 volvo vnl 780

Discussion in 'Trucks [ Eighteen Wheelers ]' started by thedutchbaker, Oct 25, 2012.

Page 1 of 2
  1. Oct 25, 2012 #1
    thedutchbaker

    thedutchbaker Bobtail Member

    36
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    Jun 21, 2012
    Hanover, PA
    0
    I have been having an issue with my air pressure not staying above 100 psi at idle.

    When sitting i can rev it up and only get it up to maybe 80psi but when traveling highway speeds i can build to governor cut off and when that happens my (F) air gauge will stay at cut off and the (R) gauge will drop. when sitting idling it will stay about 68psi just above the Low Air Warning alarm.

    Recent repairs done before issue: (Made by Mechanic)
    Tractor Protection Valve replaced, and Rear Air Ride leveling valve taken apart and serviced and inspected by mechanic (same one that replaced the Tractor Protection Valve) because he said the frame was too high.

    Repairs since (Made by myself)
    Air Dryer Filter changed
    Air Dryer Turbo Replaced (Was leaking)
    Safety Manifold replaced (Was Leaking)

    any ideas, happy to get questions for me to answer if you need more information.
     
    thedutchbaker, Oct 25, 2012
    thedutchbaker, Oct 25, 2012
    #1
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  3. Oct 25, 2012 #2
    flood

    flood Road Train Member

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    will it hold psi when the trucks off...?
     
    flood, Oct 25, 2012
    flood, Oct 25, 2012
    #2
  4. Oct 25, 2012 #3
    WMGUY

    WMGUY Road Train Member

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    Jan 1, 2011
    Nine Mile Falls, WA
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    i just had both air manifolds replaced on mine

    it would bleed off in a few minutes before
     
    WMGUY, Oct 25, 2012
    WMGUY, Oct 25, 2012
    #3
  5. Oct 25, 2012 #4
    Heavyd

    Heavyd Road Train Member

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    If you have an ISX you could be leaking air at the turbo actuator solenoid located below the air compressor, the air line to the turbo, or the actuator itself. The engine has to be running for this, or the solenoid will not open. You could also have a massive leak at the fan clutch that will only get air with key on. What engine do you have? Does this leak continue with the engine running or not? The "R" gauge will be all secondary systems. This will include air ride, cab ride and air accessories.
     
    Heavyd, Oct 25, 2012
    Heavyd, Oct 25, 2012
    #4
  7. Oct 26, 2012 #5
    Pablo-UA

    Pablo-UA Road Train Member

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    Borispol, Ukraine
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    if you have cummins engine check VGT actuator for air leak. To be sure block 8 mm air line to engine.

    If you have Vovlo engine check EPG and solenoid/actuator for air leak.

    Engine is noisy and you cant hear air leak noise, when engine is off - no leak. Usually truck makers use accessory air tank (in EU tank #4) to supply engine air actuators, but not Volvo, they use tank #2 (secondary).
     
    Pablo-UA, Oct 26, 2012
    Pablo-UA, Oct 26, 2012
    #5
  8. Oct 26, 2012 #6
    flood

    flood Road Train Member

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    if you have a volvo engine this will sound dumb but us volvos have a air valve for the jakes..
     
    flood, Oct 26, 2012
    flood, Oct 26, 2012
    #6
  9. Oct 26, 2012 #7
    Pablo-UA

    Pablo-UA Road Train Member

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    Oct 11, 2010
    Borispol, Ukraine
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    not US volvos only. EU cabovers too) LOL
     
    Pablo-UA, Oct 26, 2012
    Pablo-UA, Oct 26, 2012
    #7
  10. Nov 1, 2012 #8
    thedutchbaker

    thedutchbaker Bobtail Member

    36
    0
    Jun 21, 2012
    Hanover, PA
    0
    it will build air until the fan cuts off and then hold while i continue to keep the fuel pedal press, but the (R) will drop down after I release the fuel pedal.
     
    thedutchbaker, Nov 1, 2012
    thedutchbaker, Nov 1, 2012
    #8
  11. Nov 1, 2012 #9
    thedutchbaker

    thedutchbaker Bobtail Member

    36
    0
    Jun 21, 2012
    Hanover, PA
    0

    That makes scense since it affects my hi/lo switch in the trans, I have the ISX 450hp, it will hold air pressure above the LAW only when prarked no more than that. it will hold air with the truck turned off.
     
    thedutchbaker, Nov 1, 2012
    thedutchbaker, Nov 1, 2012
    #9
  12. Nov 1, 2012 #10
    tuckerthetrucker

    tuckerthetrucker Bobtail Member

    45
    70
    Sep 3, 2011
    south dakota
    0
    I'll second checking your fan clutch.
     
    tuckerthetrucker, Nov 1, 2012
    tuckerthetrucker, Nov 1, 2012
    #10
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