changing o rings /seals/guides at cotrol valves loader backhoe

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This topic contains 5 replies, has 3 voices, and was last updated by  Kenneth Lutz 3 years, 6 months ago.

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  • #25796 Reply

    I wanted to change out the seals and O rings and guides in the control valve assembly area right on the machine. First question has anyone challenged this on the machine, Second one is, it is constantly leaking, should I drain the main tank first before dropping down spool shaft so all sorts of a rush of oil will come out ? There are other questions but I will wait till I have a better idea what to proceed. This is a New Holland LB 620 machine.

    #28482 Reply


    I have no experience with this machine but I can offer this: if the valve you’re working on is located lower than the hydraulic tank then you’ll probably need to drain it. also check if the tank is pressurized (like on an excavator) usually there will be vent mechanism built into the tank cap… or just remove the cap. Sorry thats about all the help I can give for this one. good luck.

    #28507 Reply

    Thanks alot Matthew for your input I will agree. Gravity above the challenged area for repair of component housings, the oil will want to at least flow out faster with spool valve removed. Its just that draining it is not a straightforward thing on this machine. I have to disconnect the draw line to pump at bottom of 2 foot tank reservoir. I am going to hook up vacuum cleaner at vent top while disconnecting. Their will be less spillage while guiding to five gallon bucket. The o rings i have never done before on spool valve area. I do not even know if o rings are on spool valve or set into housing.

    #28508 Reply


    Actually you just reminded me about a little gizmo I picked up from my local CAT dealer, It’s called a Vacuum Transducer (I can’t remember the part number off hand) It’s an awesome little tool that you attach to the top of the hyd tank and then plug your air line into and it creates a negative pressure on top of the oil therefor trapping it in the tank. The advantage over a vacuum cleaner is that the transducer won’t actually suck out any of the oil from the tank, very cool tool!

    Mine cost me about $70 CAD

    once again good luck

    #28688 Reply


    hook up vacuum to tank .you have to get replacement cap drill hole thread and install a fitting that you can hook up to vacuum pump. pull 20 plus inches of vacuum but should hold hydraulic fluid in tank so you can remove spool from valve

    #28857 Reply

    Thanks P. Dis not realize you answered. And thanks for input. Good idea and I used a vacuum cleaner to change out a leaking no close valve on a 275 gallon oil #2 and it sucked in walls with some bangs of steel shifting so I lessened it by some air leakage in were it was taped to breather tube and ran that while I replaced fitting with a half a tank of oil in it. So this idea does definitively work. I have three more spools to pull and service. It has been two weeks already and still on first spool. Having a lot of issues with it just in refitting new O rings and inserting spool back in and it shears o rings smaller. Modifying spool valve and going smaller on O ring too (metric). Thanks for great input. Ken

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