International vari touch

Discussion in 'Classic Machinery' started by Mur Huwcun, Sep 3, 2015.

  1. Mur Huwcun

    Mur Huwcun Member

    Location:
    North West Wales
    Hi, having bother with the hydraulics on a Bradford 276. Lift etc stopped working altogether with position lever but would work when you pushed the draft spool on top link bracket. Removed top to strip chest down, found spool sticking. Cleaned up and refit, lift now works but will lift no weight or produce pressure at tipping pipe.

    Again by pushing draft spool arms will lift to top or blow relife valve if tap is closed and strain engine which shows pump is ok as is the PRV or am I missing something simple here? Have checked all linkage and the chain inside top. By now it's baffling me!!! Any help much appreciated!
     
  2. Tractortech

    Tractortech Member

    Location:
    Cumbria
    Now Then..
    What's a Bradford 276??
     
  3. possibly a bomford
     
  4. Tonym

    Tonym Member

    Location:
    Shropshire
    McCormick International 276 built in the old Jowett factory at Bradford in the late sixties.
     
    Angus likes this.
  5. Mur Huwcun

    Mur Huwcun Member

    Location:
    North West Wales
    Sorry, yes as above Bradford built tractors like the 250,275,276,414 and 434 as opossed to the later Doncaster built world series 74,84 series etc
     
  6. Mur Huwcun

    Mur Huwcun Member

    Location:
    North West Wales
    Had another play with this one over weekend, PRV must be ok as it will strain engine when it's blowing by manually moving the draft rod. If it was lift cylinder seals then I should be getting pressure at trailer tipping pipe by isolating cylinder but still can't. Any one have a manual at all for the hydraulics? The tractor workshop manual does not give much detail about the lift valve etc
     
  7. Rob Smith

    Rob Smith New Member

    I’ve got a similar problem with the vari-touch on my B275. Hydraulics were slow, but now the arms will only lift with absolutely no weight - I can easily stop them with just one hand! And there’s no pressure at the tipping pipe. But like you I seem to have pressure at the pump.
    Did you find out the cause of your problem - or source a manual?
     
  8. Have you checked to see if the orifice filter is clean, as this is where your problem started,

    The hydraulic system is it 2 half's, a high pressure high volume half, and a lower pressure low volume half,
    When you push in the draft spool from the back, this bypasses the low pressure/volume half all together, and as you will find , it will pump oil and blow the relief valve off at full pressure, so high side is fine,

    The low side is a very good design and we'll thought through valve chest, 1 of the first, if not the first, that lifts on a balance pressure, this means it will not lift the Hyd arms whatever ever the weight is on them without any drop when lifting, ,
    This works like this, let's say there is 600kg on the arms, and you want to lift it from half way up, to the top, when you move the leaver up, the low pressure side comes in to force and builds the pressure up and moves the internal oil activated control spool, once the pressure is balanced it will lift the ball off it's seat, and lift the hydraulic arms without any drop, till they reach the position high selected then spool returns to neutral, and the ball sits back on its seat to hold it there,

    Now if shite gets into the low pressure side, then you will have the symptoms your having, it takes next to nothing to upset it, carefully remove and renew the orifice filter, if this don't sort it, then it's a take apart and clean and good luck with that, it's not the easiest of jobs,,

    An other way to clean it without taking it a part, is drain all the oil, fit new suction filter in the oil feed to pump, and put some 32 hydraulic oil mixed with diesel 50/50, and run for a while, this might flush the dirt out
     
  9. Mur Huwcun

    Mur Huwcun Member

    Location:
    North West Wales
    Hi, No I didn’t get much further with this I stuck a battery on the tractor this summer to move it and they seemed to be working better!!

    I did strip the chest down initially to clean it, was starting to think then that it was the valve behind the feed pipe into the valve block but that did not change anything either. Your explanation of low pressure side makes sense and with mine it was a slither of silicone that I found in the main lift spool!! Will have to sort it out this winter and then finish the 275 and then re start the 250 project and do something with the 434 engine and maybe just build a shed for them all!!!
     
    Pennine Ploughing likes this.

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