Problem with Lazer Z HP hydraulics

Discussion in 'Mechanic and Repair' started by kman91, Jun 24, 2013.

  1. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Kman...you seem to be having some trouble wrapping your mind around the concept that pressurized hydro fluid can cut into and erode steel..
    Normal pressure between the valve plate and the head is around 1200 psi..thru a fairly large opening..
    Think of a pressure washer...1200 psi would be like using the tip with the largest hole...and thus..the lowest pressures..
    Now..reduce the tip size to the diameter of a scratch...the pressure increases a bunch...
    Just like blowing a hole in your driveway with water..
     
  2. ricky86

    ricky86 LawnSite Bronze Member
    Posts: 1,701

    Eh... like something coming up out of the wheel motor perhaps.
    Only a gambling man would repair that pump (or replace) without inspecting the motor. And yes, it could break a peice of spline off and still work.
     
  3. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    I thought about that..till I enlarged the pics...
    Anything large enuf to wipe out the metal between the ports...would have trashed the valve plate..
    There is only 1 damaged slit on the plate...that...along with the absence of anything more than metal powder...
    Led me to the conclusions that I reached....a failure that got worse over hundreds of hours..
     
  4. kman91

    kman91 LawnSite Member
    from Houston
    Posts: 23

    If something cracked off inside the motor, it would seem like a good flush would take care of what cracked off, unless there was more to come, right?

    Has anyone taken the wheel motors apart? Is it more/less tricky than the pump? Do they have seal kits for that too?

    Thanks again guys!
     
  5. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Just for kicks...if you still have the old hydro filter...cut it open and see if it caught anything...
    I doubt you'll find anything more than silvery crud...
    Flush the wheel motor with 1 qt of the hydro fluid you are using.,.
    Insert 1 hose into the jug and 1 hose in a bucket...turn the wheelmotor by hand until it has cycled the quart..
    Look for debris in the bucket...Also..remove and wash out the hydrotank..and blow thru the bypass hoseswith air,,
    Thats bout all you can do...should be as good as any high dollar repair shop...
    Time to get that mower back in the grass....getter dun....
     
  6. kman91

    kman91 LawnSite Member
    from Houston
    Posts: 23

    I've inspected the valve plate under magnification and it looks almost like it's coated on that one side with some sort of plating. During the whole ordeal, the plating came off in the area of the slit (where the damage is evident). I'm almost wondering if the plating was bad and caused the damage, or if the plating came of as a result of cavitation or high temps and caused the damage, or contributed to it.

    I also noticed that the back of the valve plate has what looks like some discoloration from heat. Is this normal? If not, it would certainly support your theory that the pump was either put together wrong, or subject to some oil starvation at some point.

    I took the head apart and inspected the valves. They looked good.

    Another thing I noticed last night is that the head has some minor gouging in the area of that damaged slit. I don't expect that will cause any trouble since oil already flows in that area (I'll smooth it a bit so no edges break off), but it is interesting.

    Thanks for all the help here! I really appreciate the expert advice! You guys have helped me immensely!
     
  7. kman91

    kman91 LawnSite Member
    from Houston
    Posts: 23

    I just cut apart the filter. Piston Slapper you were right, just a small amount of tiny silvery flakes.

    The filter was dated 1/1/12 (handwritten), so it looks like it was changed then.
     
  8. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    I guess my guesser is workin purty good...
    If that is all the metal that the filter caught in a year and a half...
    Its safe to say that whatever initially damaged the pump happened before that..
    Rebuild the pump and cut some grass...

    BTW...the new valve plates do have some blueing on them...normal...
     
  9. ricky86

    ricky86 LawnSite Bronze Member
    Posts: 1,701

    If part of the motor got lodged in the valve plate, it would explain the gouging in the cylinder block, between the ports Failures happen quick in hydrostatic pumps. Cavitation...... I don't think so. Take the motor apart and prove me wrong.
    And just so you know, between the plate and the cylinder block, that's where you're high pressure is. Any leakage between the two, operating temps will skyrocket. Cavitation is usually caused by an inlet restriction. A poor design can cause problems, but that's not the case here. If cavitation was the case, what about the other pump? Same supply system. I'm not getting into a debate. Your machine, your call. But my suggestion leaves no doubt. The brand we sell always wanted the motors disassembled for cleaning after a pump failure. They never paid enough, but that's another story altogether. If there was a brg failure, a flush is "usally" suffecient, Anything else, rip it. Good luck
     
  10. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,240

    Ricky....not gonna debate...im sure you know what you know...

    I dont know the history on this mower either...
    Maybe someone previously replaced this pump..and cranked it up dry ???
    Im just having a problem with so much damage to the ports on the cylinder block..and so little damage to the valve plate.???
    The cylinder block is constantly held against the valve plate...if metal got between them...theyd both be chewed up...
    Nothing i like better than a puzzle with pieces that dont fit....
     

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