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Thread: manitou 526

  1. #1
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    manitou 526

    friend of mine just bought a manitou 526 3000hours.has a hydraulic problem,when he crowds the headstock right back the boom starts to lift.the boom it self is very slow lifting and when it is under load starts to lower.any ideas?

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    Senior Member T P's Avatar
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    Re: manitou 526

    My idea would be that you have found why the previous owner just sold it, I'm sure ACE will be along shortly to put you out of your misery, I'd be thinking to block off the compensating ram if it has one and see if that cures it or alters the symptoms in which case the compensating ram needs new seals or an arv is set lower than the main relief valve pressure. I've only worked at a couple of Manitou's and I'm not familiar with that model.ACE will know more no doubt.

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    Re: manitou 526

    In my experience, it's a 'manitou' so sell it quick before it breaks you in the pocket and spirit!! Probably some ram seals and a valve or two adjusting at best, at worst my first comment applies!

  4. #4
    Senior Member ACE's Avatar
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    Re: manitou 526

    Quote Originally Posted by mathew tsa View Post
    friend of mine just bought a manitou 526 3000hours.has a hydraulic problem,when he crowds the headstock right back the boom starts to lift.the boom it self is very slow lifting and when it is under load starts to lower.any ideas?
    How old is it?

    When you crowd the carriage hard back the small compensation ram will take weight off the main lift ram and show up any wear in the boom lift ram pin and bushes. These models are very prone to wearing bottom lift ram bushes right though and knackering the ram eye.

    If your compensation ram is lifting boom right up and pulling rod out of the lift ram then you have a problem with lift ram seals and lock out valve.

    Hyd pumps are prone too wear on these too will cause slow hydraulics and hard steering at idle.

    Another thing too look at on this model is the boom mounting to chassis pin and around the compensation ram mounting lugs both ends as they are prone to cracking and pulling right off.
    Late machines I think are slightly improved in this area.
    To help relieve stress in this area I lower the pressure relief valves on the tilt circuit by 30 bar or so. They are set higher than main pump pressure which I see no reason for.

    You also should educate the operators in to not lifting or lowering the boom allowing the tilt ram to be at the end of its travel as this puts maximum stress on the compensation ram mountings.

    I think main pump pressure is 250 bar on these models if you wanted to check that. Sounds bit like you may have 2 or 3 issues to me?

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    Re: manitou 526

    Quote Originally Posted by ACE View Post
    How old is it?

    When you crowd the carriage hard back the small compensation ram will take weight off the main lift ram and show up any wear in the boom lift ram pin and bushes. These models are very prone to wearing bottom lift ram bushes right though and knackering the ram eye.

    If your compensation ram is lifting boom right up and pulling rod out of the lift ram then you have a problem with lift ram seals and lock out valve.

    Hyd pumps are prone too wear on these too will cause slow hydraulics and hard steering at idle.

    Another thing too look at on this model is the boom mounting to chassis pin and around the compensation ram mounting lugs both ends as they are prone to cracking and pulling right off.
    Late machines I think are slightly improved in this area.
    To help relieve stress in this area I lower the pressure relief valves on the tilt circuit by 30 bar or so. They are set higher than main pump pressure which I see no reason for.

    You also should educate the operators in to not lifting or lowering the boom allowing the tilt ram to be at the end of its travel as this puts maximum stress on the compensation ram mountings.

    I think main pump pressure is 250 bar on these models if you wanted to check that. Sounds bit like you may have 2 or 3 issues to me?
    Hi ACE, I wish i had seen this page earlier. We've been having trouble with our 627, when you crowd it right back and lower you would get a sharp jolt. Which Im assuming is the compensator ram pressure relief valve releasing and the weight of the boom coming on to lift ram. There is some play in the bushes but not an excessive amount i would say. My dad seems to think its because the bushes are worn?? He does know not to crowd it back and lower but today we had a disaster and the chassis has completely cracked behind the compensator ram where the compensator ram has been trying to force to apart. My dad does a lot of heavy digging of soil with a big bucket on and over loading it. what do you think has caused this? In hindsight I wish I had reduced the pressure relief vale but didnt know that you could or where it is?

    thanks

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    Senior Member ACE's Avatar
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    Re: manitou 526

    Quote Originally Posted by tubeofglue View Post
    Hi ACE, I wish i had seen this page earlier. We've been having trouble with our 627, when you crowd it right back and lower you would get a sharp jolt. Which Im assuming is the compensator ram pressure relief valve releasing and the weight of the boom coming on to lift ram. There is some play in the bushes but not an excessive amount i would say. My dad seems to think its because the bushes are worn?? He does know not to crowd it back and lower but today we had a disaster and the chassis has completely cracked behind the compensator ram where the compensator ram has been trying to force to apart. My dad does a lot of heavy digging of soil with a big bucket on and over loading it. what do you think has caused this? In hindsight I wish I had reduced the pressure relief vale but didnt know that you could or where it is?

    thanks
    Known issue. Its just weak area and driver abuse. There is a mod kit from manitou for persistant offenders! To add in a seperate inline relief valve to the compensator circuit. Never seen one fitted though.

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