Harbor freight crane jack leaking

The hydraulic jack on my crane has two problems:
1) it leaks around the small (pumping) cylinder 2) When I open the valve, it opens too abruptly, so the crane drops
instead of going down slowly, I totally hate this.
So. I would like to buy a replacement jack, preferably something of "high quality", chrome plated cylinders, made in USA or some such. Are there any suppliers who sell similar but better jacks?
Pictures are here:
http://igor.chudov.com/projects/Harbor-Freight-Truck-Crane/
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus16322 wrote:

Igor, you can rebuild yours (just needs a seal or O-ring or two) or you can simply buy another one from HF. This time, I'd get an air/over/hydraulic one like this one:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber562
I haven't seen a US manufactured 8 ton long throw jack in many years.
Grant
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Grant, I need a much smaller 3 ton one (12 inches retracted). Your jack is for a 2 ton shop crane, whereas my issues are with the truck crane. I will call HF for a rebuild kit or replacement. I think that they have one. I definitely do not need air over hydraulic.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 18 Aug 2008 01:15:07 GMT, with neither quill nor qualm, Grant

I was going to suggest that, but it's on the back of his pickup.

Compare the length of that beastie with the (5" ram travel) jack in the 37555 crane Ig has, Grant. <g> http://www.harborfreight.com/manuals/37000-37999/37555.PDF
-- It is pretty hard to tell what does bring happiness; poverty and wealth have both failed. -- Kin Hubbard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 17 Aug 2008 18:35:00 -0500, with neither quill nor qualm,

So learn some dexterity, Ig. <gd&r> Alternatively, you could use the winch to lower the load instead of the hydraulics. <g>
Additionally, mill a large diameter lever or round knob/cap for the valve stem and pop it on when you want to use the valve.

I've seen some nice air-overs but they're all 8-T and long bodied, built for the shop cranes, not the truck cranes.
-- It is pretty hard to tell what does bring happiness; poverty and wealth have both failed. -- Kin Hubbard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Larry, I think that you are mostly right. The problem is that when the boom is raised high, the wire rope hangs on the bottom lengthwise slot in the boom, beneath the roller, instead of being suspended from that roller.
I took the boom to my mill and lengthened the slot by an inch, which will hopefully enable the winch to work even when the boom is fully raised.
If so, then, I will be able to use the winch at those elevations.
Also, on the hydraulic front, I added a cross "T" handle to the hydraulic handle. I practiced a little to close the valve by holding the body of the handle, so that I would not overtighten it, and open it by holding on to the T.
This does not solve the leaking issue, but it solves all other issues.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 17 Aug 2008 21:45:39 -0500, with neither quill nor qualm,

_Notch_ that puppy.

Oh, you did that already. ;) Good.

Alternatively, use the winch to take up all slack and raise the load as far as possible, then use the hydraulics to finish raising it to the necessary level.
Or cut of that roller bracket and weld the damned thing on the front where it belonged in the first place. <shrug>

Excellent idea.

Control is everything! Didn't your crane come with a valve kit? Pick one up at HFT.
-- It is pretty hard to tell what does bring happiness; poverty and wealth have both failed. -- Kin Hubbard
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus16322 wrote:

Every bottle jack & hydraulic engine hoist I have ever seen will leak if stored with the valve closed, you might try to park it with the valve cracked open 1/4 turn or so & see if the leak stops.
MikeB
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
quickly quoth:
snip

snip
Iggy,
I just purchased the same Harbor Freight crane for our Biology Department's pontoon boat, and ran into the same problem with the cable rubbing on the slot's lower end at high arm elevations. I can't figure out their concept in the cable switch-back on the rollers...cable over the far side on the top roller and the near side of the bottom. ??? It looks like whoever designed it, never actually saw it in use. Or, more likely, someone in manufacturing misread the print and drilled the top hole in the wrong location...over and over, and over again. :(
So, as opposed to your solution, I elongated the hole under the top roller, in the direction of end of the arm, about another 3/4". This allowed me to ran the cable on the far side of both rollers. Now the length of the slot under the bottom roller makes sense, and I can get full elevation without interfering with the cable.
I have pictures, if this isn't clear.
Ken
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ken, it is clear. I also wondered about that design
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
quickly quoth:

If you go the repair route, once you get your leak fixed, restrict the oil passage to limit the down speed...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Look at this web site http://thehardwarecity.com /. It has good products on this topic.
Ignoramus16322;1380471 Wrote:

--
ipc_781

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I had a similar problem with an 8 ton shop crane. I bought it from Northern Tool (formerly known as Northern Hydraulics. They sold me a Kit that didn't even come close to fitting. The piston was so sloppy when I took it apart that I brought the jack back to them. They didn't care. They offered to sell me a new, USA made jack, which I bought. It has worked well for 3 or 4 years now. It is double acting!. Not happy with Northern Tool for not standing behind the original jack, but they told me that they no longer carry the Chinese model that failed. Maybe they have on in the size you need.
Pete Stanaitis -----------------------
Ignoramus16322 wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wrong set of pictures.
Is there an oring under the nut surrounding pumping piston? If so, replace.
Wes
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Oops, didn't see the jack in the corner of lift.
Wes
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Aug 17, 7:35pm, Ignoramus16322 <ignoramus16...@NOSPAM. 16322.invalid> wrote:

You might try disassembling it to flush out any machining debris, and filter the oil through a paper coffee filter. I've had better luck reassembling hydraulics with Teflon paste rather than tape.
That round lump on the side that looks like a rivet is the rubber oil filler plug.
A knurled 2" knob makes them easy to control. I press an aluminum disk onto a 1/2" steel rod.drilled and slotted to fit over the existing release. 2" is probably large enough to overtighten the needle valve if you aren't careful.
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus16322 wrote:

overkill it for a resonable price you can get a 20 ton in that size, short throw or long. HF has them, I need one to level a house.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If you can pump it up, but it drops down quickly, you may have air in the system that can be purged out when you add more jack oil. Chinese hydraulic actuated tools are notorious for developing leaks. If you remove the jack from the crane, you should be able to put it on its side and find and remove the air bleed plug. If you pump the jack part way, you can more easily add jack oil in this hole. Cycle the ram up and down, and make sure that you have a pan or rags to catch any overflow. Jack oil can be obtained from your local auto parts store. Maybe theyll have this version: (Amazon.com product link shortened) (Sometimes Ill use automatic transmission fluid as a substitute.)
Lots of people are stuck with cheap floor jacks that they feel that they should be able to repair, but just cant find parts. Ive taken apart floor jacks and re-assembled them with o-rings or homemade seals with middling success. If you disassemble yours, make sure that you keep track of the parts and dont loose the ball bearing or spring for the check valve. Ive spent hours hunting one down after it rolled under the workbench.
Its interesting to see how theyre assembled anyways. I found pictures of someone rebuilding a floor jack here: http://www.garagejournal.com/forum/showthread.php?t=18055&page=4 This one shows what looks like cup seals and leather backing. The seals that are on pumps vary, but this gives a general idea of what you might expect if you start disassembly. Some real old-time jacks used leather, rope or string packing that could be compressed with a sleeve and gland nut similar to what was found on older gate valves or water pumps: http://www.diybob.com/diyPackingGland.htm http://www.monarch-mclaren.com/leather.htm
Ive still not figured out why most Chinese jacks fail. Im not sure of the materials used in their seals. (Nitrile (Buna-N) should be the best choice.) Could be poor fit up and excessive clearances cause the seals to extrude and fail prematurely. Ive cleaned out machine chips that caused the balls on the check valves to leak. Could be a bad seat where the ball fits in the check valve. In that case, the pump doesnt hold its position under load. Bad pump design might pull the piston out too much causing it to wobble and prematurely stretch and wear the seal.
Some people have tried to make a go of supplying repair parts for imports, but it doesnt seem profitable: http://www.hyjacks.com/H32.HTM
Good primers on jacks: http://www.hyjacks.net/animation.htm , http://www.hyjacks.com/H7.HTM
Background on hydraulic jacks and repairable brands: http://www.hyjacks.com/H2.HTM , http://www.jackxchange.com /
Hydraulic seal types: http://www.sealing.com/hydraulic-seals / Hydraulic seal materials and failure modes (industrial): http://www.epm.com/faq.html
If I were to re-build another jack, I might get some hydraulic seals or rod seals from McMaster Carr or machine a new pump with a packing gland.
Different company from the one quoted above. (These guys claim to sell parts that will fit the imports, but I havent used them, cant vouch for them, and it might be a pricey gamble for what you are trying to fix): http://www.hydjack.com/krk305.html
Lots of people say to save time and money by buying only good quality products. Theyre probably right, but I still like figuring out what goes wrong and why.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I ordered standard metric cups that fit the cylinder bore and machined adapter bushings to fit them to the piston. The piston and cylinder were soft and easily machined to a good finish. You can also order piston rod and cylinder stock from Bailey, http://www.baileynet.com /
Jim Wilkins
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.