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Sullair 375HH Compressor Oil going out the Air Lines

Discussion in 'Other Construction/Demolition Equipment' started by mechman1, Jun 4, 2020.

  1. mechman1

    mechman1 New Member

    Feb 5, 2020
    Hey folks,
    I have a customer with a Sullair 375HH that is losing compressor oil out the airlines. In my experience, it is often the Oil Air separator element that causes this. However, this unit was serviced about 200 hours ago with an OEM Separator...but... there is a puddle of oil on the "dry" side (inside) of the element.
    On a second, yet tied together question, there is a clear nylon tube running from the front end right-hand side of the compressor head that goes to the receiver tank, and hooks to a stem that goes into the center of the separator element. Sullair calls that the oil return line...??? I have questions about that, as that is the dry side of the element.
    Any help that the combined experience here can give would be great!
    Thanks folks.
  2. MarshallPowerGen

    MarshallPowerGen Well-Known Member

    Nov 27, 2017
    Diesel & Generator Mechanic
    Coeur d'Alene, Idaho
    Usual suspect is the machine being shut off with air valves still open.

    The "stem" should be your oil scavenge tube, check that it didn't get bent straight down through the center of the filter. They're supposed to be slightly offset and pick up the oil puddling from the inside of the element.
    mg2361 likes this.
  3. Kelly Gruell

    Kelly Gruell Member

    Aug 26, 2020
    Lewiston, Idaho 83501

    Also on some models the scavenger lines that pick up the oil from the bottom of the seperator tank and send it back to the screw end of compressor. Look at any fittings on the scavenger lines and make sure the are sealed, they need to act like a vacuum line. If you have two site glasses when running one should show oil flowing through it and the second one should have no oil. we always ran a three way valve with one gauge 60 to 120 PSI and had one attached to seperator tank and one to line pressure. this way you could tell why running the filter differential pressure between filter more accurate.