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plow won't lift under load when hot... :(

Discussion in 'Truck & Equipment Repair' started by vintageauto, Jan 2, 2010.

  1. vintageauto

    vintageauto Junior Member
    Messages: 3

    Hello all, this is my first post here. I have an older Arctic 7 1/2 foot hydralic snowplow, power lift and angle (hydralic) with the monarch hydralic powerpack (M683 I think) and my problem is that it gradually gets slower lifting as it gets warmer/using it, to the point where it will not lift the plow. (as i'm using it it lifts less and less higher, as well as slower, to the point where i can't get it off the ground) I assumed it was the fluid bypassing the cylinder packing/seals, so I just replaced the lift cylinder and hose with a brand new one. It seems to be marginally better, but am still gradually losing lift. I am using Dextron ATF fluid, as per Monarch/arctic recomondations. Fluid is clean and like new. I have made sure fluid was right up, numerous times. The hydralic pump/motor all seem to work fine, and I always have full power at angling, hot or cold (i can move the truck with the angle!) Plow is on a 1991 GMC 1/2 ton suburban 4x4. Lift cylinder will lift to it's limit without plow hooked up when warm, but will not lift the plow off the ground, or if it does, barely. Any help greatly appreciated. I have all the manuals, etc, as well as the hyd powerpack complete manuals. Thanks in Advance...
  2. Willthethrill99

    Willthethrill99 Junior Member
    Messages: 2

    Same problem- arctic plow monarch pump motor

    Did you get your problem solved with your plow in 2010? I have same problem plaguing me all winter and had plow and truck sold and plow quit lifting at all once it warms up and only has 600 psi pressure from pump when hot and over 1000 when cold
    Lifted blade 50 times before bringing to buyer and than would not lift for buyer and needed about 10lbs lift by hand to lift
    Also losing side to side but not sure if its the pump or motor??
    Any advice is appreciated
  3. basher

    basher PlowSite Fanatic
    from 19707
    Messages: 8,993

    Sounds like hydraulic power supply problems to me. 1000 psi isn't near enough pressure 2K is more the norm. Yes the fluid's viscosity changes would effect pressure.

    Beware, don't just start throwing parts at it. It could be a weak pump, a weak pressure relief valve, maybe a coil/valve acting up. IMO a little diagnostics with a pressure valve would be in order :nod: or you could just keep buying parts.:rolleyes:
  4. Willthethrill99

    Willthethrill99 Junior Member
    Messages: 2

    Arctic plow

    Thanks Basher,
    Today i drained the thinner Boss plow fluid that I accidentally :jester:bought instead of recommended Trannie fluid and it worked perfectly for 70 lifts in 15 minutes with dextron trannie fluid mixed with a little sae30 oil for testing purpose.
    I than drove around for 30 minutes as the engine heat seemed to add to the problem, and sure enough when i tried to fully lift and lower 10 more times the pump/motor sounded much weaker and blade raised slower every lift until it finally wouldnt lift again.

    We have checked pressure on output on all lines even at 600psi (hot) and had a mechanic check the relief valves and he indicated the pressure would not increase by adjusting either.
    the mechanic is pretty sure its the pump and i'll ask him about a pressure valve if its different than the pressure gauge he used on all outputs while adjusting relief valves.

    How do we test for the coil-valve being possible culprit?
    Also, could the pump motor be getting weaker when heated up with under-hood engine heat? It was really torquey and louder when cold, but advised more likely the pump which is much more expensive than the monarch 8112 motor driving the pump.
    I surely dont want to unnecessarily throw parts at it and appreciate all advice!
  5. basher

    basher PlowSite Fanatic
    from 19707
    Messages: 8,993

    Typo on my part that should have read pressure gage.:blush2:

    I would agree with the man with the gage (boots on the ground) replace the pump.