M720 pump replacement or rebuild

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asajay

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I obtained an M720 at auction a couple years ago and it sat idle until today when I wanted to hook it up to an S280 shelter I have. However, I found both hydraulic pumps to be non-operational, so I didn't dare lower it to the ground to start with. Both pumps move easily without ever building any pressure (yes, the pump valve is in the Pump position). My knee-jerk reaction is that the seals are probably bad.

Question:
What is consensus on the best way to fix this? Can the pumps be rebuilt? Are there suitable replacements available?

Thank you,
Asa Jay
 

gimpyrobb

dumpsterlandingfromorbit!
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The pumps if memory serves are parker something-50 pumps. Should be rebuild-able.
 

asajay

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So a kit like this might help?:
M720 pump rebuild kit.png

Do you have any experience rebuilding these? If so, how easy would you say it is? I've done plenty of mechanical rebuilds, so I feel this falls in my wheelhouse; just looking for any "gotchas." :)
Thank you,
Asa Jay
 

asajay

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I ordered up a couple of kits. I've got next week off work and this looks like a good project for a day or two. :) I'll try to post my rebuild here.
Asa Jay
 

Coug

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Most hydraulic pumps I've ever worked on were very simple. There really isn't a whole lot to most of them, so hopefully these are the same.
Good luck, take your time, and pay attention to what direction the seals are facing when you take it apart.
 

asajay

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I'm finally getting to the teardown of the first pump. I have it all apart at this point. Next job is to try and remove three coats of CARC from the housing, two of which are flaking off badly. I'm not sure if I should sandblast or use heat and a scraper. Any recommendations?

I had an evil thought of taking the housing down and have it anodized or ceramic coated, instead of just trying to paint it.
Any thoughts about that?

I'm taking lots of photos, and a few notes. I'll be posting more hopefully in the next week as I find time to continue.
Asa Jay
 
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Coug

Active member
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28
Location
Olympia/WA
I'm finally getting to the teardown of the first pump. I have it all apart at this point. Next job is to try and remove three coats of CARC from the housing, two of which are flaking off badly. I'm not sure if I should sandblast or use heat and a scraper. Any recommendations?

I had an evil though of taking the housing down and have it anodized or ceramic coated, instead of just trying to paint it.
Any thoughts about that?

I'm taking lots of photos, and a few notes. I'll be posting more hopefully in the next week as I find time to continue.
Asa Jay
Carc is some pretty nasty stuff, so scraper would probably be safest, though I normally pressure wash it to keep the dust down. If it stays on after a few good passes of high pressure, I leave it alone unless it's got obvious bubbles under it where it's trying to come off, then I use a plastic scraper and pressure wash it some more.

Whatever method you choose to use make sure to wear breathing protection, CARC is some nasty stuff, and you really do NOT want to breath in any of the dust.
By breathing protection I recommend full face type respirator, not just a cheap dust mask and glasses.
yes, it IS that nasty.
 

asajay

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Thank you for the pointers about CARC.

I got to looking at the kit of parts last night real quick and noticed the kit for the Enerpac P51K1 is not exactly right. Some parts in the kit are correct, other parts aren't for this pump, and parts from this pump that are needed, aren't in the kit.

There is a large number cast into the bottom housing but I'm not sure it's for the overall assembly or not. It's "Part No. D1063-800." I'll be doing more research today when I have a chance. I'll get back to the pump on Thursday night, and I'll try to post photos either late tonight or tomorrow night.

Edit: a bit more research this morning. Looking through the TO, I found a reference on page 5-10 to a KU2000 parts kit for this pump. Now to see if I'm able to find one and see what's in it versus the p51 kits I got earlier.

Asa Jay
 
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asajay

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Spokane, WA
Investigation results.
Looking up kit part number of KU2000 on NSN sites, I found the kit was made by a couple of different manufacturers. The NSN is
4320-00-304-3925

The manufacturers are:
Actuant Corp.
Komatsu America Corp.

I left a message with Enerpac which is/was Actuant Corp or a division thereof, I forget. I was concerned that the NSN description did not call out all the necessary ball bearings and seals. Enerpac actually got back to me quickly. They identified the pump as a derivative of the Enerpac P307-2. They said the kit part number should be KH2505 and is still a good part number. They referred me to their distributor page to find someone who might sell me one. I contacted a local pump rebuilder in Spokane to see if they had one but it was close to closing so I expect I might hear back tomorrow. I otherwise have been unable to get a full description, but I did write Enerpac back asking for exactly what's in the kit. I have a concern the Enerpac piston is larger than what I have and the top seal/nut isn't the same. That being the case, I may have to simply take the old worn out parts to a local supply, like a Grainger maybe and see if I can piece the parts together.

Here is a photo I found on the Internet of the P307-2 with a part label affixed:
P307-2 hydraulic hand pump 1.jpg

Here you can see the huge piston size:
P307-2 hydraulic hand pump 2.jpg

Here is a photo of the victim I'm disassembling; note the much smaller piston size here:
100_3380.JPG

Here are all the parts that came out. Note the large slotted nut on the left with two packing rings to the right of it. These came out of the top case where the piston goes in. This appears to be a different size than the Enerpac model:
100_3397.JPG

I have an email out to Komatsu (the other manufacturer listed in NSN). Maybe they'll show me something different. I found new Enerpac P51 models sell for upward of $600 each. At that price I can find alternatives (not the same shape or size) for a third of that, with even more psi capabilities. Although I'd like to return this model to working condition, I'm not against just replacing it all if inexpensive enough.

I'll update as I find out more.
Asa Jay
 
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