Suspension wont build air when under the load

Discussion in 'Kenworth Forum' started by Mokhtar, Dec 7, 2023.

  1. Mokhtar

    Mokhtar Bobtail Member

    Mar 20, 2013
    I have a 2017 Kenworth T680. If the trailer is empty its no problem but when I am loaded the air won't build. It takes long time used to be two minutes driving before it will build, now it longer even 10-20 minutes. I don't hear any air leaks, but it burns a lot of fuel.

    Also the fan won't shut off, but again only when I'm loaded. If I'm hauling empty trailer its fine.
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  3. 062

    062 Road Train Member

    Oct 20, 2013
    Might be the pressure protection valve stuck partially closed.
    I don’t know which one it has. You can google pressure protection valve and get a idea of what you’re looking for.
  4. Big Road Skateboard

    Big Road Skateboard Road Train Member

    May 2, 2021
    Sounds like you're not building air pressure. That's why your fan stays on too. I'd bet you have a major leak somewhere under a load.

    Big air leaks make little noise
    JB7 Thanks this.
  5. PaulMinternational

    PaulMinternational Heavy Load Member

    Aug 23, 2022
    You have an air leak someplace, a valve stuck, a bad air assisted fan clutch would be my most likely guess by your description.

    Unplug the wires for it, this should make it not ask for air. If its leaking that will make your bags work normal until you plug it back in.
  6. 201

    201 Road Train Member

    Apr 16, 2014
    high plains colorado
    Gremlins in the machine,,,:eek:, okay, you got at least 3 things going on here. I don't think they are related. Could be an air leak, but you'd hear something. Ride height valves do go south, fan running while loaded sounds like a plugged radiator, and they all use a lot of fuel. If you aren't building air, could the brakes be dragging?
  7. JB7

    JB7 Medium Load Member

    Dec 13, 2022
    Agree. After ruling out/ repairing any air leaks I would check the leveling valve. Check that the linkage connections are not worn. Can also disconnect the linkage and operate the valve by hand. And the Pressure Protection Valve like 062 said.

    blairandgretchen Thanks this.
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