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Peterbilt 379 air brake system problem

Discussion in 'Trucks [ Eighteen Wheelers ]' started by jared l morse, Nov 3, 2015.

  1. Nov 3, 2015 #1
    jared l morse

    jared l morse Bobtail Member

    2
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    Nov 3, 2015
    0
    I have replaced the air dryer and Gov. On my 379 it is still purging too often (about every 30 seconds) due to two air leaks out of the top of the compressor: at around 120 PSI the safety valve on top of the compressor starts popping and makes a knocking sound as it purchase air from the valve on the head and also leaks air from a small plate held down by two screws located adjacent to the safety valve but this system still makes 130 PSI at which time the perch valve on the air dryer pops but due to the leaks at the head of the air compressor the pressure bleach down too fast causing the purge valve at the air dryer to continuously pop about every 30 seconds during vehicle operation.

    Oil sprays out of the air tanks in a fine mist and air dryer purges unusually high amount of water.

    Does this mean that there is an internal problems with the air compressor?
     
    jared l morse, Nov 3, 2015
    jared l morse, Nov 3, 2015
    #1
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  3. Nov 3, 2015 #2
    Oscar the KW

    Oscar the KW Going Tarpless

    12,246
    28,114
    May 19, 2011
    0
    Sounds like a new air compressor is in your very near future.
     
    Oscar the KW, Nov 3, 2015
    Oscar the KW, Nov 3, 2015
    #2
    Ozdriver Thanks this.
  4. Nov 3, 2015 #3
    drdesl

    drdesl Light Load Member

    218
    388
    Oct 7, 2015
    Billings, Montana
    0
    Cat or Cummins? On the Cats, the unloader valve in the head will get gummy and cruddy and stick. Easy repair with new parts, brushes, brake clean, etc. On a Cummapart, the unloader is internal in the head and not accessible. you would need a new compressor cylinder head at a minimum. God, I love Cats.
     
    drdesl, Nov 3, 2015
    drdesl, Nov 3, 2015
    #3
    Ozdriver and jared l morse Thank this.
  5. Nov 3, 2015 #4
    jared l morse

    jared l morse Bobtail Member

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    Nov 3, 2015
    0
    cat C13
     
    jared l morse, Nov 3, 2015
    jared l morse, Nov 3, 2015
    #4
  7. Nov 3, 2015 #5
    drdesl

    drdesl Light Load Member

    218
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    Oct 7, 2015
    Billings, Montana
    0
    Then it should be serviceable.
     
    drdesl, Nov 3, 2015
    drdesl, Nov 3, 2015
    #5
  8. Nov 3, 2015 #6
    Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    If you get oil out of the tanks and other problems you're better of getting a new or reman compressor. They aren't that expensive considering that if decides to go offline you're immobile.
     
    Ozdriver, Nov 3, 2015
    Ozdriver, Nov 3, 2015
    #6
  9. Nov 3, 2015 #7
    Ozdriver

    Ozdriver Heavy Load Member

    767
    1,390
    Oct 16, 2015
    Australia
    0
    The unloader valve in my 3408 caused the psi to go to 160, it was more or less disintegrated. I thought it was governor at first but replacing that didn't make any difference.
     
    Ozdriver, Nov 3, 2015
    Ozdriver, Nov 3, 2015
    #7
    drdesl Thanks this.
  10. Nov 3, 2015 #8
    mtoo

    mtoo Road Train Member

    1,928
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    Jan 15, 2011
    Retired on bended knee
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    I like it when somebody says; "my 3408"
     
    mtoo, Nov 3, 2015
    mtoo, Nov 3, 2015
    #8
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