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Fisher MM1 - Pump Problems

Discussion in 'Truck & Equipment Repair' started by 86turismo, Aug 17, 2015.

  1. 86turismo

    86turismo Member
    from home
    Messages: 31

    Hi All,
    Well it's getting to be that time of year again where I live to get the plow ready. I started with changing the fluid.

    I removed the hydraulic lines for the left and right rams so I could push the blade around and remove all of the fluid from the left and right rams. I drained all of the fluid from the main reservoir. I replaced the hoses and drain plug for the reservoir. I filled the reservoir until fluid ran out the hole on the side of the reservoir. I then moved the plow left, right, up and down and rechecked the level in the reservoir assuming I would need to add more fluid once the fluid filled the rams. I did have to add a little more. Filled it until it ran out the hole on the side of the reservoir. Moved the pump few more time in all directions. Then the pump started squealing and the plow will not move.

    Any thoughts on what the issue may be? The plow is older and pretty rusty. I am not able to remove the bolts that hold the pump on the reservoir.

    Any suggestions you may have are appreciated!

    Thank you for reading and for responding!

  2. dodgegmc1213

    dodgegmc1213 Senior Member
    Messages: 997

    Sounds like you over filled it and it hydro locked, always go to the first threads in the insta act pumps (if thats what you have). I did that once on the old pumps and it hydro locked and couldn't move, started unscrewing the fill plug and it popped off with fluid shooting out, it then became free. So easily take the plug out and see if it shoots fluid out.
  3. 86turismo

    86turismo Member
    from home
    Messages: 31

    I pulled the level plug and a little fluid ran out. Not much more than an ounce or so. I left the drain plug out over night just to be sure everything that would come out did. I left it for about a week.

    Also right after I changed the fluid and filled (over filled) while changing it I could not push the head down, being pretty sure the plow was in float mode. I had read on this site before that some times the nut on the rams can get over tight or "sticky", so I thought I would loosen the nut to see if that would help with the head not going down when the plow was in float mode. I got the nut loose and fluid squirted out, so I guess I was a little over full. I put the nut back in place and let the plow for a few more days.

    Then last night I went out just to see what would happen. I hooked up the plow and everything worked as it should. I could move the plow fully extended in all directions, and also I could push the head down all the way.

    Thank for the advice about the pump potentially being hydrolocked. This forum has been a valuable asset to a greenhorn plow guy with an old plow on top of now experience. You guys are great!!

    I have attached a picture of my joystick and pump.




  4. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,743

    Just fyi, when you check the fluid level, blade is straight and the lift ran is all the way down.