how to bleed the hydr. clyinder on a dump

Discussion in 'Trucks [ Eighteen Wheelers ]' started by earthmover, Jul 18, 2011.

  1. earthmover

    earthmover Medium Load Member

    Messages:
    403
    Thanks Received:
    13
    Joined:
    Jan 27, 2009
    Location:
    castalia , north carolina
    hey guys i have been bleeding my dump truck cylinder while the bed is down .. i just open up the bleeder and let any air of fluid run out and close it...there most be a way to do it so that you dont have any air trapped in the system...cause after a mth or so i have air in the system again and again...how am i suppose to bleed it???? do you bleed it wiht the bed up on the pins..i have a site tub and its about 2" down from full and has been that way for years now...thanks mike
     
  2. Les2

    Les2 Road Train Member

    Messages:
    5,151
    Thanks Received:
    2,236
    Joined:
    Jul 25, 2008
    Location:
    kicked back in my lazyboy...
    Automatic bleeders, thats what all the dumps I pulled had.
     
    123456 Thanks this.
  3. Mr. Haney

    Mr. Haney Road Train Member

    Messages:
    2,721
    Thanks Received:
    1,963
    Joined:
    Dec 17, 2008
    Dump cylinders always allow air to enter them. When you let the body down always put the control lever back in the neutral position. Most dump truck drivers leave the control in the down position this allows fluid to return to the tank if the packing rings on the cylinder leak slightly. The weight of the fluid wants to return to the lowest point in the system(the tank) if the packing rings allow air past them the fluid gravity feeds into the tank and the air is at the highest point, the cylinder. To bleed a dump body correctly whether it's a dump truck or dump trailer is to raise the body fully, then lower it to within 6" of lowered. Hold the body at this position while bleeding the air off at the top of the cylinder. This way you've raised the cylinder fully and allowed the air to get trapped in the last stage of the cylinder. When you lower it to 6" from the frame rail, you still have the weight of the body being supported by the cylinder and creating pressure to push the air to the top. You can then get into the body and to the top of the cylinder safely to bleed it. If you don't bleed all the air before the body comes to rest..........repeat the whole process until you no air coming from the bleeder.

    The cylinder may need the packing rings tightened, but take the truck to a hydraulic shop to do this properly. If you try to do it yourself you can have problems in how the cylinder stages raises and lowers...........this can be very dangerous with the dump body dropping a complete stage of the cylinder while trying to raise it under a heavy load or the dump body not coming down properly after dumping a load
     
    123456 and SL3406 Thank this.
  4. Mr. Haney

    Mr. Haney Road Train Member

    Messages:
    2,721
    Thanks Received:
    1,963
    Joined:
    Dec 17, 2008
    I hate the dang gone things..........they always seem to allow oil past them to make a mess of the truck and trailer
     
  5. Pablo-UA

    Pablo-UA Road Train Member

    Messages:
    6,995
    Thanks Received:
    1,273
    Joined:
    Oct 11, 2010
    Location:
    Borispol, Ukraine
    air in dump cylinder makes PTO pump work with zzzzz sound, but it is normal.
    Dupm truck system is self bleeding system, like PS system, and do not use autobleeders, truck looks greazy! the only good thing with automatic bleeders - oil on frame inhibits rust)))
     
  6. Les2

    Les2 Road Train Member

    Messages:
    5,151
    Thanks Received:
    2,236
    Joined:
    Jul 25, 2008
    Location:
    kicked back in my lazyboy...
    Wasn't my trailer so it wasn't my choice. It never failed anyway, I'd always have a cylinder that leaked a little so the bleeder was of no worry.

    But it did work.
     
  7. earthmover

    earthmover Medium Load Member

    Messages:
    403
    Thanks Received:
    13
    Joined:
    Jan 27, 2009
    Location:
    castalia , north carolina
    i think i found the problem when i let the bed down i can hear air under the truck so i got under the truck and think the line from the lever to the pum may have a small hole it it ill know for sure tomm.. getting dark now thanks oh my truck has a manual bleeder that i have to pull the cover and turn a small bolt with t hole in it...also it was repacked about 4yrs ago...now when it comes down sometime the last stage will go back up and hit kinda hard from time to time thats how i know it has air.. i bleed it and its good for a while but it is scary and dangerous.. thanks mike:biggrin_25524:
     
  8. Les2

    Les2 Road Train Member

    Messages:
    5,151
    Thanks Received:
    2,236
    Joined:
    Jul 25, 2008
    Location:
    kicked back in my lazyboy...
    Had one drop one scope and slam the deck while I was standing there taking a wiz once....

    Good thing I already had it out of my pants!:biggrin_2559:
     
  9. Jfaulk99

    Jfaulk99 Road Train Member

    Messages:
    2,918
    Thanks Received:
    1,573
    Joined:
    May 16, 2009
    Location:
    Couch
    Dude you drive a Freightliner! Everyone expects it to have oil all over it, under it, all over the driver (especially his hair).
     
  10. Les2

    Les2 Road Train Member

    Messages:
    5,151
    Thanks Received:
    2,236
    Joined:
    Jul 25, 2008
    Location:
    kicked back in my lazyboy...
    :biggrin_2559::biggrin_2559: