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Airbags not equalizing properly

Discussion in 'Trucks [ Eighteen Wheelers ]' started by riles0340, Jul 10, 2022.

  1. Jul 10, 2022 #1
    riles0340

    riles0340 Bobtail Member

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    2020 367 tri drive. The passenger side airbags will not air up to the same pressure as the driver and they'll deflate on their own. Can't figure out why. I've had it into multiple different shops including couple different peterbilts, and they all just replace the compensator. It never fixes the problem. I have override and it will fill and dump.the bags but normal ride height will not hold on its own. Anyone had this issue before?
     
    riles0340, Jul 10, 2022
    riles0340, Jul 10, 2022
    #1
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  3. Jul 10, 2022 #2
    AModelCat

    AModelCat Road Train Member

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    Single or dual levelling valves?
     
    AModelCat, Jul 10, 2022
    AModelCat, Jul 10, 2022
    #2
  4. Jul 10, 2022 #3
    AModelCat

    AModelCat Road Train Member

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    How's the truck loaded? With a single levelling valve it'll lean to the heavy side. Dual valves should hold it level since left and right operate independent of each other.

    Have seen some goofy things happen in dual valve setups if the valves are mismatched. Some valves react faster and some react slower. They'll fight each other if they aren't matched.
     
    AModelCat, Jul 10, 2022
    AModelCat, Jul 10, 2022
    #3
  5. Jul 10, 2022 #4
    riles0340

    riles0340 Bobtail Member

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    Single leveling valve. When the truck is loaded it doesn't seem to do it, only when it's empty. When there is air in the passenger side there's a very noticeable difference in how much less it has compared to the drivers side.
     
    riles0340, Jul 10, 2022
    riles0340, Jul 10, 2022
    #4
  7. Jul 10, 2022 #5
    riles0340

    riles0340 Bobtail Member

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    It's always loaded level. Seems like it's a supply issue to that side
     
    riles0340, Jul 10, 2022
    riles0340, Jul 10, 2022
    #5
  8. Jul 10, 2022 #6
    AModelCat

    AModelCat Road Train Member

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    How about the front end? A lean to one side at the steer axle can translate to issues noticed on the rear.

    Has anyone put a gauge on the bags on each side yet to verify if the air pressure is indeed low on the passenger side?
     
    AModelCat, Jul 10, 2022
    AModelCat, Jul 10, 2022
    #6
  9. Jul 10, 2022 #7
    riles0340

    riles0340 Bobtail Member

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    The front is level. No need for a gauge as you can tell from touching it. The right side you can see and feel that it's a deflated bag. If I hit the switch and dump the suspension and raise it again, both side will come up equal. After a short time the right side will deflate, almost like a check valve or something is letting the air past. I can't hear anything leaking one it levels. Is there a check valve somewhere between the leveling valve and the bags?
     
    riles0340, Jul 10, 2022
    riles0340, Jul 10, 2022
    #7
  10. Jul 10, 2022 #8
    AModelCat

    AModelCat Road Train Member

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    That's honestly a good question. I always thought all the bags were tied together off of one common outlet on the levelling valve. That may not be the case on this newer stuff.
     
    AModelCat, Jul 10, 2022
    AModelCat, Jul 10, 2022
    #8
    Shawn2130 Thanks this.
  11. Jul 17, 2022 #9
    loudtom

    loudtom Road Train Member

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    I've got a spread axle trailer that does the same thing between the front and rear axles. I think it has something to do with the dump valve, possibly a check valve integrated into the manual dump switch. When it's loaded it has no problem, but it acts up while empty. If I dump both axles and refill them it will work properly. Hard braking while empty also causes it to act up. Eventually the bags will level out, but it is constantly exhausting air until then.

    If mine were acting up from side to side, I would swap air lines on the bags so that it acts up from front to rear.
     
    loudtom, Jul 17, 2022
    loudtom, Jul 17, 2022
    #9
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