1. Welcome to PlowSite. Notice a fresh look and new features? It’s now easier to share photos and videos, find popular topics fast, and enjoy expanded user profiles. If you have any questions, click HELP at the top or bottom of any page, or send an email to help@plowsite.com. We welcome your feedback.

    Dismiss Notice

MM1 Piston rebuilding

Discussion in 'Fisher Engineering Discussion' started by MRBachand, Sep 11, 2009.

  1. MRBachand

    MRBachand Senior Member
    Messages: 198

    My lift piston packing seal is half on the somewhat rusty shaft, and half in the pack.

    It has been off a few years, but now its way worse. Moisture is defanately getting in there, as I freeze at least twice a winter.

    I want to tackle this before winter.

    What is the process of rebuilding the lift piston?

    SHould I emery cloth the piston down, or replace?

    How tough is it to get this 12 year rusty weathered by nature item apart?

    Torches? (??)
     
  2. SuperdutyShane

    SuperdutyShane PlowSite.com Addict
    Messages: 1,517

    You must have a friend with an old plow around the yard you can steal the lift cylinder off :D My plow didnt come with angle pistons but a friend had about 50 of them haha. Good luck.
     
  3. Crash935

    Crash935 2000 Club Member
    Messages: 2,377


    With all that said, whats the price differance between and new nut with seal, piston and your time versues buying a new lift cylinder?
     
  4. MRBachand

    MRBachand Senior Member
    Messages: 198

    The lift cylinder is permanately one part of the power-pack, including ressevoir and all that. If it was just a cylinder like the angle ones, i'd just get a new one without thinking twice...

    All that work sounds above me for my first time, h owever, it is still september, so i have time to get into trouble...

    How long would it take a pro to cut and rebuild using your above method?
     
  5. MRBachand

    MRBachand Senior Member
    Messages: 198

    With all that said too, whats the worst that will happen using a slightly pitted upper shaft, and a non sealed packing seal? Moisture in, or total lift failure?
     
  6. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I've never worked on one of these, but once you had the packing nut off, couldn't you disconnect the piston from the lift arm and use the pump to push the piston out?

    As for getting the packing nut to loosen, try Fluid Film. Let it sit a week or better.
     
  7. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Use the same method for removal on the SHEP unit.

    A pitted ram and non sealing packing will just let water into the pump and cause freeze up. The "i keep it in a heated garage" trick wont work either, once you get it out in the cold it can freeeze up at anytime and usually right at the time you need it to go up the most.

    A pro could probably do it in a couple of hours, a air saw really makes a differance when it comes to cutting the packing nut.

    Like COR said, it doesnt hurt to try a penetrating oil several times over a week or 2 to help loosen things ups before you try cutting everything out.
     
  8. MRBachand

    MRBachand Senior Member
    Messages: 198

    I think Its going to come off no problem. I am going to order the new packing nut, new rod assembly, and new packing kit w/wiper.

    Once I undo the packing nut, and remove the packing kit, does the rod assembly (piston) unscrew? or does it just lift up and out?

    If there was nothing stopping the lift arm from lifting, would it push itself right up and out? (off subject question of mine)

    I have the SEHP power pack, where lift cylinder is part of the resevoir base.

    Here is a blow up.

    http://www.fisherplows.com/pdf/20751_031203.pdf


    For what its worth, I have teh SEHP 10" 2500 Commercial (the big boy) :)
    As always, thank you sincerely for your help.
     
    Last edited: Oct 11, 2009
  9. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    On page four in your link, look at part 24. Split bearing. That should be what keeps them from coming out.
     
  10. MRBachand

    MRBachand Senior Member
    Messages: 198

    So that bearing hits the packing nut then?

    Thanks, so once the packing nut is removed, all of that will just pull out by hand?

    Now that I'm looking at things closer, my piston is pitted pretty good at the top, (out of use normal use range) and its just the wiper ring that is a little bit out in one small spot.

    If you were to replace this piston, what parts would you order?
     
  11. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Well, you could tear it apart and see exactly what you need.

    But I would order 19, 20, 21, 22, 24. If you want to order the piston 23, go ahead. But if there is no pitting in the service area there is no need.
     
  12. MRBachand

    MRBachand Senior Member
    Messages: 198

    So its just a matter of undo-ing the packing nut (toughest part of the job?) removing everything by hand, re-placing the parts and sliding it back in and cranking down the packing nut?
     
  13. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    That's what it looks like to me. Did you put the FF on the packing nut?
     
  14. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Dont over tighten the packing nut.
     
  15. MRBachand

    MRBachand Senior Member
    Messages: 198

    I put Pbblaster around the nut .. Probably wont get parts for another week or so (mail order) so I'll hit it a few more times ...

    Another question.

    If I just choose to replace the wiper ring, that must be right under the packing nut, so loosen packing nut, replace wiper ring, and retourque the packing nut?

    Are packing nuts usually re-useable if you do not have to cut them off?

    How tight do you crank these packing nuts? Just snug? With a big ol' wrench it seems it may be easy to overtighten.
     
  16. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    You will have to dissassemble the entire unit to replace even just the wiper. You could try going down over the top of the piston, but would likely damage the wiper. There is no reason you cannot reuse the packing nut. As long as it spins nice and freely in the cylinder.
     
  17. MRBachand

    MRBachand Senior Member
    Messages: 198

    Shoulnd't have said that... I'm past the point of no return now. I scraped the crud out, blew it clean, and positioned it so PB BLASTER can pool around it. I will leave it this way refreshing the PB once a day . Saturday I will try to remove it furthur.

    Any ideas guys?

    Packing nut 001.JPG

    Packing nut 003.JPG
     
  18. MRBachand

    MRBachand Senior Member
    Messages: 198

  19. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    Now you went and did it, done broke it right off!!!!

    A little heat from some MAP gas atleast wouldnt hurt. Wiper seal should already be in the new packing nut.
     
  20. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I would try heating the nut as hot as you can get it, then spray it with cold water. This will do two things. The shock cooling will help break any corrosion between the nut and cylinder. It will also help harden the nut. Do this a few times. The last time I would spray Seafoam Deep Creep or Fluid Film on it. After it has cooled down, spray with FF or DC.

    Do the whole routine for a couple of days.