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MM2, plow won't turn when down & blade can move by hand, swings while driving

Discussion in 'Truck & Equipment Repair' started by chrisg00, Nov 28, 2014.

  1. chrisg00

    chrisg00 Junior Member
    from boston
    Messages: 6

    I have a Fisher MM2 plow. Used it for a storm on Wednesday. Worked great most of the time however I noticed towards the end of the night it wouldn't angle right if it was lowered, only if it was raised. It is still doing it for the most part. If there is no snow in front of the blade when it's down, it will angle right. But if i have even a little in front while pushing it, it will not angle right, must be lifted up a few inches from the ground.
    Now I am noticing that while driving the truck with the blade fully raised, after a few minutes the blade will start rocking between left and right angle. I can get out of the truck and manually turn it with my hand. I though that the hydraulic pistons would prevent me from moving the blade?
    There are no signs of any fluid leaks, lines look good, pistons look good, seals look good. Not sure how to check the fluid level. I removed the threaded plug and can see there is fluid in the pump but no level indicator.
    Any help is greatly appreciated.
  2. cl733

    cl733 Senior Member
    from Canada
    Messages: 263

    you must not have fluid on each side of the piston head to allow it to rock back and forth like that angle the blade all the way one way and take the return line off the ram and run the pump to try and push it more to see if you have oil going past the piston ive seen that happen with a loose hose and it sucking air into the ram if it isn't in the piston heads then maybe in valving , your reservoir should be about 3/4 full if you have been sucking air then that could be your problem too
  3. chrisg00

    chrisg00 Junior Member
    from boston
    Messages: 6

    Thank you.
    I will give that a try tomorrow.
  4. South Seneca

    South Seneca Senior Member
    Messages: 474

    Sure sounds like air in the system.