air bags problem -help needed

Discussion in 'Trucks [ Eighteen Wheelers ]' started by AUSSIE DAVE, Apr 8, 2011.

  1. AUSSIE DAVE

    AUSSIE DAVE Road Train Member

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    my air bag suspension works good, except when i got loaded recently, by the time the forklift finished loading (forklift repeatadly drives inside the shipping container while the container is on my truck) there was no air left in any of the air tanks and no air left in the airbag suspension. When i started the truck to drive away it took forever to build air because the airbag ride height adjustment kept leaking air while trying to pump up. but with taking the RPM up to 1500 the airbags did pump up and then the leak stoped and stayed good. this has happened 3 times with three very heavy loads, it only happens in this situation, at all other times the airbag system works great. ANY IDEAS ???
     
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  3. Jfaulk99

    Jfaulk99 Road Train Member

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    It should have a protection valve that won't allow any air to the suspension unless the air tanks are above like 80psi. It's in case you blow a bag your brakes won't set. I would sometimes dump the tractor/trailer when loading so the truck would still have enough air to release the brakes and move out of the way when they were done.
     
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  4. Pablo-UA

    Pablo-UA Road Train Member

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    Air bags have separeted with protection valve tank. There is no gauge usually, there are rear and front pressure gauges in cabine only.

    The other reason to have protection valve - that pressure in air suspention tank may be higher then in brake tanks, especially if it is 4x2 trucktor.

    So firs of all find air suspention tank, add a gauge and check pressure.

    Also inspect and if necessary replace protection valve.

    Air systems of trucks differ. So what is your truck, whay year of make?
     
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  5. freightlinerman

    freightlinerman Road Train Member

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    I would venture to guess your leveling valve is leaking. Spray your air bags and lines going to the air bags with soapy water.

    Remember, the leveling valve is a CHECK valve even if your truck loses all air pressure it should still hold the air in the bags unless its bad or your air bags are leaking. Listen for leaks.
     
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  6. Superhauler

    Superhauler TEACHER OF MEN

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    next time you load or unload flip your dump valve switch and dump the air that way the bags are not airing up and down all the time.
     
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  7. freightlinerman

    freightlinerman Road Train Member

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    The only time they will be airing down is unloading. When loading, they should be filling with more air.
     
  8. Jfaulk99

    Jfaulk99 Road Train Member

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    Not when the forklift drives in (bags compensate) then backs out (bleeds off).
    Here was his quote:
     
  9. freightlinerman

    freightlinerman Road Train Member

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    There shouldn't be that much air loss even for that.
     
  10. Jfaulk99

    Jfaulk99 Road Train Member

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    Depends on how long the lift is in there on each trip, if he has a delay or non-delay leveling valve, how much air the truck had when they started........ Too many variables to just give a "can't happen" answer. Just dump them before they start and eliminate the issues.
     
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  11. AUSSIE DAVE

    AUSSIE DAVE Road Train Member

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    Thanks all, ok here is more info based on what you all have said. The forklift goes in and out about 20 times with heavy goods, truck is a kenworth 1998 T401 short nose bonnet 6x4. air is leaking from ride height adjustment valve were it dumps air from. When trying to build air back up after forklift has finished it only leaks air from one side (one ride height valve). every time the forklift goes into container you can see the air gauge loose pressure. I replaced the other ride height valve about a month ago because it was broken, so one of them is new and one is old. thing is it only leaks in this situation and once i eventually build air to about 500kpa in front tank it stops leaking and is normal again. but building air up to 500kpa takes a long time (and at 1500RPM) because there is so much air leaking out of the ride height adjustment valve
     
    Last edited: Apr 8, 2011
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