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  1. #1
    Gold Member
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    Oct 2003
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    465
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    Northern California
    Tractor
    New Holland TN70S

    Default Changed hydraulic fluid - now don't have any hydraulics...

    I'm sure this is an easy one, but I couldn't find anything in my owners manual that points me in the right direction - so obviously I come back to TBN.

    I just changed out my hydraulic fluid and all the filters on my TN70S, and now I have no hydraulics. I drained fluid from all the places the manual told me (from the main resevoir, from under the 3-PH arms, and from the 4WD housing), and filled up the filter as much as I could before reinstalling it. I'm sure I need to bleed the system - is there a bleed screw someplace on the hydraulic pump? What's the proper procedure for bleeding the air out?

    Thanks in advance for any help!

    Martin

  2. #2
    Veteran Member gordon21's Avatar
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    Feb 2006
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    1,005
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    Lake Lure NC
    Tractor
    JD 790

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Did you start the engine and cycle the FEL controls? If you have power steering, then turn the wheel lock to lock a couple times. Raise the 3PT hitch up and down a couple times. Then go check the fluid level again. Chances are you will be a quart or more low.
    Lewis Gordon

    JD 790, 300 FEL, 5' KK rotary mower, 5' boxscraper, Huskee 3PT logsplitter, JD#39N sickle mower and a Jinma 6" chipper in JD colors.

    My XUV gas Gator wants a brother !!!!!!!! (the diesel kind)

  3. #3
    Gold Member
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    Oct 2003
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    Location
    Northern California
    Tractor
    New Holland TN70S

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Thanks very much for the quick reply! Yes, I did cycle the power steering to each side a couple of times. Unfortunately I can't cycle the 3PH because I have a backhoe installed and the arms are under the backhoe assembly.

  4. #4
    Veteran Member gordon21's Avatar
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    Feb 2006
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    Lake Lure NC
    Tractor
    JD 790

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Even better you have the backhoe mounted. Cycle all the backhoe functions back and forth. You have a couple gallons of OLD fluid in the hoe that did not get changed. You now have probably 4-5 gallons of new fluid and 2 gallons of OLD fluid that will intermix once the system is bled. If you have a FEL, you also left a gallon or two of old fluid in those hoses and cylinders. There is no way short of dismantling all your hydraulics to change the oil completely.

    Change what you can and move on. If the old oil bothers you, do another oil change and you will get rid of 80% of the old oil and 80% of the new oil and you will STILL have some of the original oil left in the system.
    Lewis Gordon

    JD 790, 300 FEL, 5' KK rotary mower, 5' boxscraper, Huskee 3PT logsplitter, JD#39N sickle mower and a Jinma 6" chipper in JD colors.

    My XUV gas Gator wants a brother !!!!!!!! (the diesel kind)

  5. #5
    Gold Member
    Join Date
    Oct 2003
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    465
    Location
    Northern California
    Tractor
    New Holland TN70S

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    I'm not too worried about the oil mixing - the oil was still pretty fresh, and the main sump holds over twelve gallons of oil that I drained out and replaced, so whatever's left in the implements is going to be outnumbered in a big way. Also, I went with kubota Super UDT this time around to better handle water content in the oil - so overall I'm not worried about mixing a few gallons of old fluid in with the new.

    Problem I'm having is that none of the hydraulic controls work at all, except for the power steering. So I'm assuming the main hydraulic implement pump is air bound and can't get a prime.

  6. #6
    Veteran Member
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    Oct 2005
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    1,432
    Location
    N. E. Ohio
    Tractor
    tc- 29d

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Is kubota Super UDT approved oil for the unit? Or should I say; does it meet or exceed specs?
    dqdave1; tc-29D; woods 7500 bh; 7308 fel, land pride tiller, land pride rake, gill pulverizer, 60"mmm. , bucket forks , MZ16H

  7. #7
    Gold Member
    Join Date
    Oct 2003
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    465
    Location
    Northern California
    Tractor
    New Holland TN70S

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Yes, Super UDT exceeds all the specs and from what I've read, it is the hot ticket for those of us that really work the heck out of our hydraulic systems. I don't have any first-hand experience yet -because the whole system is sitting idle while I try to figure out what's keeping my hydraulic system asleep.

  8. #8
    Silver Member
    Join Date
    Oct 2004
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    125
    Location
    Knoxville, TN
    Tractor
    NH TC29D

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Did you add new oil and start the engine, then check the oil level? Let the engine run for awhile and it will get the air out and should work. Or let it sit over night, then try it. I will come around and work soon, don't worry. Maybe it's just tired and wants a break from work.
    2003 NH TC29D Hydro 4x4, 914A 60" Belly Mower, 7308 FEL, 5' King Kutter Rotory Cutter, 60" Midwest Box Blade, Woods 7500 Backhoe. www.4x4TractorWork.com

  9. #9
    Epic Contributor
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    jinman's Avatar
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    Feb 2001
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    21,014
    Location
    Texas - Wise County - Sunset
    Tractor
    NHTC45D, NH LB75B, Ford Jubilee

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Quote Originally Posted by mahlers
    Yes, Super UDT exceeds all the specs and from what I've read, it is the hot ticket for those of us that really work the heck out of our hydraulic systems. I don't have any first-hand experience yet -because the whole system is sitting idle while I try to figure out what's keeping my hydraulic system asleep.
    You don't want to run that hydraulic pump for very long without fluid. It will self-destruct without fluid for internal lube and cooling. Letting the tractor set overnight and trying again is a good choice, but I think I'd check with my dealer's service manager to see if they have some tricks. It might be as simple as slightly pressurizing the reservoir, or opening a line somewhere to bleed out the air.

    I'm sure you have a separate power steering pump and reservoir, so that will do you no good to cycle that.
    Jim


  10. #10
    Elite Member JC-jetro's Avatar
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    Jul 2006
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    3,192
    Location
    Kansas
    Tractor
    Ford 1700, Kubota MX-4700

    Default Re: Changed hydraulic fluid - now don't have any hydraulics...

    Quote Originally Posted by mahlers
    I'm sure this is an easy one, but I couldn't find anything in my owners manual that points me in the right direction - so obviously I come back to TBN.

    I just changed out my hydraulic fluid and all the filters on my TN70S, and now I have no hydraulics. I drained fluid from all the places the manual told me (from the main resevoir, from under the 3-PH arms, and from the 4WD housing), and filled up the filter as much as I could before reinstalling it. I'm sure I need to bleed the system - is there a bleed screw someplace on the hydraulic pump? What's the proper procedure for bleeding the air out?

    Thanks in advance for any help!

    Martin
    Martin,

    I think your pump is cavitating. Gear type positive displacement pump are not designed to pump or compress air. You must get the air out of the system by bleeding it. The inlet pipe to the pump is almost always the larger diameter than the discharge. If you have a banjo pump connection on the inlet I loosen it up to see if I start seeing fluid. Obviously this will only work on siphon principal... the fluid height in the reservoir should be higher than the pump inlet to induce flow.You probably see combination of air and oil to come out of banjo fitting collect the oil in a clean container so you can return it to the reservoir. By doing so you are priming the pump. if the pump manages to get a slug of oil moved in the pipe ... then the vacuum action will suck the flow toward the pump inlet. Pump initially needs to be primed. Only diaphram or reciprocating pump with spring loaded intake and exhaust valve are able to self prime. As Jinman indicated refrain from running the pump dry. you will destroy the pump quickly without proper lubrication, oil film coefficient can only help damage for a short time.

    JC,
    Ford 1700, 2wd.
    Kubota MX-4700DT, Gear transmission with LA 884 loader, Q/A and HD bucket.
    60" Woods Rotary Cutter, home made (3-pt boom and a Row Hipper) ,King Kutter( 5 ft Tiller,Middle Buster,Single Row Cultivator,Carry-all, 5 ft blade, 6 ft Landscaping Rake ,30" Dirt Scoop and a 4'x4' Drag Harrow)

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