How do I disassemble/fix a HAWE hydraulic valve on my Maho MH600E?
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  1. #1
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    Default How do I disassemble/fix a HAWE hydraulic valve on my Maho MH600E?

    All,

    Finally I have had some progress on my MahoMH600E. After switching the whole controller with the guy in this thread with a similar machine we now have both machines working. Meaning I'm now able to start the controller and make the axes move. He's able to make his machine work with my controller that I wasn't able to get to work on my mill, and I'm able to get my machine running with his. He is even using his machine to make money now by boring engine blocks for cars.

    But now I have serious problems with the hydraulics for the ATC. After a thorough cleaning one of the valves started to leak out through the coil. Therefore I attempted to take it off to see if I could make it work again.
    But this ended in disaster, and after putting it back I now have one more problem. The pump now starts every 3rd second, and runs for about .5 seconds. This indicates to me that there is a leak. But this leak isn't possible to see. There is no oil leaking except for the one drop of oil an hour that the first mentioned valve had in the first place.

    Could this come from air trapped in the system? I had to empty out all the oil, and I'm sure some air went in the hoses.

    I could try to get as much of this air out of the system, but I have removed most of it already by manually pushing the valves to make the cylinder go back and forth some times. And it now feels as if there is no more air in the system. But the pump is still turning on and off in quick succession.

    But the main question is how to disassemble the valve? I found the national supplier for HAWE here in Norway, and they could sell me a new one. But it wasn't cheap I can tell you that. About $500 is a bit more than I would like to spend on this. Especially since the leak isn't that big.
    Anyway, he expected it to be the o ring between the coil and the valve that made the initial leak. He even gave me the size of o ring to use (28 mm * 1.5 mm). My problem is I'm not familiar with hydraulic valves like these, and I have no idea on how to take it apart. And there is no evident way to take it apart as far as I can see. I would expect the valve and coil to be possible to be parted. There are also two screws that seem to keep the two parts together. But after removing the screws there was still no way the two parts would come apart. Is there a trick here, or a special tool or something I need to take it apart? I did apply some force to try to get it apart, but I gave up when it only felt like I was making things worse.

    I have looked for these valves on ebay, but so far I haven't had any luck. Apparently most other machines use other configurations of valves. The valves on my machine are VP1G. Here is the datasheet.

    The four o rings sitting between the valve and the main block were clearly old, and should probably be replaced as well. They were deformed by being squashed together for so long, and possibly don't make a good seal anymore. I will try to get the correct ones. The local supplier only had a softer version that I suspect won't withstand the pressure used.

    The question now is what to do..... I could probably live with the initial leak, as it's only a drop now and then. The problem then is how to prevent it from starting and stopping like it is doing now.

    So any advice on how to proceed would be very welcome right now. Hydraulics is the one discipline I'm leas familiar on when it comes to these machines.

    Regards
    Anders

  2. #2
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    I'm answering my own posts again.....

    I finally found something to help me out. The Swedish distributor was kind enough to give me an exploded view of the valve. That was all I needed, and I found out how to get it apart.

    I also found out that I probably didn't damage anything by trying to force it apart the last time I tried to take it apart. I was afraid I had caused more damage by trying to force it apart without removing all the screws. But from the drawings I found out that the way I applied force shouldn't damage anything.

    Now I need to order new o rings for it, and hopefully that should fix it.

    I hope I'm able to get rid of the problem with the pump starting and stopping too often by bleeding off all the trapped air in the system.

    Too bad there is no pressure gage on this system. That would definitely have helped here. I think I will try to put one on there.

    I'm really excited now, because I'm finally getting some proper progress here.

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    Less than a year ago I bought a new HAWE valve for an MH600e from a place in North Carolina for about $90. This was the valve that had something to do with the tool release....perhaps yours was a larger one ?

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    Bought new check valves for the Hawe hydraulic pump that is on the FP3NC i am rebuilding. They were pretty reasonable as i recall, but it took them two tries to get me the correct part....
    Cheers Ross

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    It occured to me to simply input keyword Hawe in my email archives and I found the exact part number and price of what I bought- Hawe DG35...new one was $92 from ETK International in Charlotte, NC USA. Matched the one in my 26 year old Maho perfectly.

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    If you have accumulator in the system that might be shot
    Had a simular item with a Hermle just 2 weeks ago

    Peter from Holland

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    You were absolutely right Peter.

    I had the accumulator checked earlier (about a year ago I think it was), and at that time it worked. But I guess it have deteriorated by sitting still for so long. And when I checked it now it blew the nitrogen out the oil port. So the rubber bladder is blown.
    Too bad this is the simple type without replaceable bladder. I had to buy a new one. I found this exact type of accumulator is used in cars. But it was difficult to find out details of them. I found some cheap on eBay, but ended up buying from an industry supplier. At least now I have one that should last for many years to come.
    The worst part of that is that I know I have one with replaceable bladder somewhere, but now I was unable to find it.


    I also used the opportunity to install a manometer to the hydraulic system, so now I can monitor the pressure in the system. I really like that. It is also useful as a safety feature. Now it's easy to know if it's safe to undo connections or if I need to bleed off the pressure.

    I was also able to disassemble the valve with a leak and replace the o rings in it. Now it's not leaking anymore. The o rings in there were really deformed by being held in the same position for a long time. And one of them had damage to it that I'm sure I didn't make. So I was able to fix that problem as well. The only issue is that the o rings I put in there were all standard 70 shore hardness. The speck calls for 90 shore hardness, but I don't think this makes such a huge difference. If I were to get the correct hardness it would take a long time, and would be a lot more expensive. If I get problems with the same valve again at a later time I will order the harder o rings. But I hope I don't have to do more about it.

    Anders

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    Thanks for keeping us posted
    It is nice to have it right once and a while

    Peter from holland

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    Dear akb1212,

    its a long time ago you posted this thread but hopefully you are stil on the forum.
    Could you make public or send the exploded view of the valve?
    If not, could you tell more about the way you disassembled the valve if you still know?

    regards toine

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    Post a picture of your valve
    I have some Hawe valves

    Peter

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    hello Peter,Thank you for answering

    I have the GZ3 and G3 for a Maho 400 P.
    The o-rings 6 x 1,5 and 3,5 x 1.2 90 shore been ordered.
    I would like to know if there are other o-rings e.g. between coil en valve part.
    They look to be connected with two screws but do not come apart after removing those screws.
    Do you know how they are connected?

    regards,

    toine

  12. #12
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    Its been too long I cannot remember (I know getting old) But did you check Hawe.com All kind of information available
    I can check monday if I have a old one lying around

    Peter

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    hello peter, you are a little bit older.
    I checked the website of Hawe and found a lot of info but not the onde I need.
    Thank you in advance for looking at a real valve.
    toine


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