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Flushing hydraulic system

Discussion in 'Forklifts/Telehandlers' started by greg9504, May 31, 2019.

  1. greg9504

    greg9504 Well-Known Member

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    Aug 29, 2005
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    Location:
    Ottawa Ontario Canada
    Hi,
    I have a 1982 Hyster H150F (15000 lb capacity). The main lift cylinder started leaking and water got into the system. I've had the main cylinder rebuilt (chrome redone $$$), so want to make sure I get all the water out of the system. Purchased new filter. So besides draining the tank and refilling with clean fluid, is there anything I can do with the hoses disconnected?
    Thanks.

    HysterH150F_liftingstone.jpg HysterH150F_removing_liftcylinder.PNG
     
  2. Tinkerer

    Tinkerer Senior Member

    Joined:
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    IL. USA
    Yes.
    If all the cylinder hoses are disconnected -------
    Begin with the cylinders at the extreme end of their stroke. Doesn't matter which direction.
    You need to connect one hose to each cylinder and extend or retract the cylinder with the machine running until the rod reaches the end of its stroke..
    That will force all the contaminated oil out of one side of the cylinder piston.
    Then disconnect that hose and reconnect the other hose. Again force the cylinder rod in the opposite direction to the end of the stroke again to expel all the contaminated oil out of that side.
    The tilt cylinders will need to be flushed also.
    Always keeping the hydraulic tank full.
    I would suggest removing the forks to lessen the chance of them causing personal injury while doing the flush.
     
  3. Tinkerer

    Tinkerer Senior Member

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    I forgot an important first step in the flushing procedure. With all the hoses disconnected from the cylinders, flush the hoses first until clean oil comes out of them.
     
  4. greg9504

    greg9504 Well-Known Member

    Joined:
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    Location:
    Ottawa Ontario Canada
    Hi,
    Thanks for the reply. Right now the main lift cylinder is out of the machine, so no chance of the forks hurting anyone :)
    I'm not too keen on running any fluid through the rebuilt cylinder until I've made a good effort to flush the system. The main lift cylinder is "single acting" but it does have two hoses/fittings (at either end). It retracts under gravity alone. It appears to me that the upper hose leads back directly to the tank, I'll have to take a closer look tomorrow, because I'm confused why a single acting cylinder has two lines. Unless the top line acts as a suction line to lubricate the rod side of the ram??

    Anyway I'll use your approach tomorrow and do an initial drain and flush and see how it goes.
    Thanks.
    If you are bored, he's a video of taking the cylinder out of the forklift:

     
  5. Tinkerer

    Tinkerer Senior Member

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    Nice video !
    Nice dog !!!
    The dead side of single acting hydraulic cylinders have to have an oil line on them. It is the only way that side of the cylinder can be kept clean and lubricated as the rod goes up and down.
    But, depending on how the cylinder is designed it may have only one line that will both pressurize the cylinder to extend it and then allow the oil flow to be reversed to let the cylinder to retract. Those cylinders rely on the weight of what it is raising to cause it to retract. A dump or semi trailer cylinder would be an application like that.
     
  6. greg9504

    greg9504 Well-Known Member

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    Well still cleaning... The hydraulic tank drain plug is a male pipe plug and it's recessed enough that I can't get a 9/16" wrench on it. So I thought I would just run oil through until it came out clear... 10 gallons later and it was still coming out looking like coffee with milk. Took the filter out, OK now I see why. It's bad. I would like to say there was someone else to blame, but I've been the owner of this forklift for the past 10 years so it's on me.

    The hydraulic oil is used for the steering, wet clutch, and the cylinders, so it's going to take a really good flush to clean it all. I'm heading to the Canadian Harbor Freight (Princess Auto) tomorrow to pick up some cheaper hydraulic oil so I can flush this thing several times. Also going to order some more filters, and have a 9/16" pipe plug socket on the way. Then I can get the tank drained and give it a good clean.

    Fun. :eek:

    dirtyfilter1.jpg dirtyfilter2.jpg filterhousing.jpg usedoil.jpg
     
  7. Tinkerer

    Tinkerer Senior Member

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    Ya Greg, The tank and the oil in it has to be spotlessly clean before you start the flushing procedure.
     
  8. greg9504

    greg9504 Well-Known Member

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    Well it's back together. As a bonus it's now rust proofed, although that wasn't my plan. A long messy job. I still need to adjust the chains but other than that it seems to be working OK. Thanks for the help.

    A view of the tank:
    cleantank.PNG dirtytank.PNG
     
  9. greg9504

    greg9504 Well-Known Member

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    Location:
    Ottawa Ontario Canada
    Here's another video of reinstalling the cylinder and what I did to flush the system, as well as testing it with ~ 13000 lb load. With hydraulic fluid and filter job cost about $3000 CAD ($2250 US), bulk of that was getting cylinder rebuilt which included having the rod rechromed.