Hydraulic Jack Repair

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Old 11-22-19, 08:25 AM
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Hydraulic Jack Repair

I have an 8 year old Central Hydraulics 1-1/2 ton aluminum jack (Harbor Freight), which has been leaking fluid for the past couple years. It's at the point now that the handle has to nearly be to the floor in order to raise the saddle. It does hold pressure once lifted, however. I didn't identify exactly where the leak was coming from (it has stopped leaking since there is hardly any fluid remaining), but my assumption is that it was leaking around the piston. Once I remove the c-clip, should the piston simply slide out? There's a large retaining collar with flats around the base, which won't budge. Being a HF jack, I imagine replacement parts aren't available. When these pistons leak, is it typically a bad o-ring that can easily be replaced with a universal one?

Also, just to be certain, is the large flathead screw the pressure adjustment and the smaller hex screw/plug the oil fill hole? That is what the sticker seemingly indicates, but it's odd to me that a large flathead screw would be used for something that shouldn't be tampered with and a small hex screw for something that requires pouring oil into.

http://www.mediafire.com/view/6hnuqz...92126.jpg/file

https://www.mediafire.com/view/6v80g...92141.jpg/file
 

Last edited by mossman; 11-22-19 at 09:48 AM.
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Old 11-22-19, 06:03 PM
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Seal

The jack might simply need bleeding, since it holds when jacked up.

This manual might be for a model similar to yours, and might give you some ideas on what to repair and the procedures.

https://manuals.harborfreight.com/ma...2999/62496.pdf

https://manualzz.com/doc/22585138/ma...ted-floor-jack

If there is a seal inside that has failed, if China made it would probably be a metric size. A farm equipment shop would probably have the needed seals. But sometimes the seal fails because the bore is not polished or has scored from some metal flashing in the fluid left over from manufacture. The new seal might not last too long, and the long stroke/quick lift feature on these jacks puts a lot of stress on the seals.

Harbor Freight has been known to replace a failed unit, even after its warranty period, so might be worth calling them to see if they would just get you a new unit.
 
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Old 11-22-19, 07:07 PM
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Thanks for the info. I removed the oil fill plug and the oil was at the top, surprisingly. I then opened the bleeding screw and slowly pumped the handle, and oil started to shoot out of the oil fill hole. There was also a ball bearing that rose to the top. I lost a little bit of oil and now the jack will not raise or hold. Worse off than I was before. Can you explain the fill and bleeding procedure for this style jack? I tried adding more oil back in, but the hole fills right up so I can't get enough oil back in.

I removed the ball bearings (there are two with a small spring in between) and I still can't get much oil in there. It fills right up and won't take anymore. Every video I've watched says to open the valve, remove the fill plug, and pump the handle to purge the air, then fill with oil. When I remove the fill plug and pump the handle, oil pushes out every time and I cannot add more.
 

Last edited by mossman; 11-22-19 at 08:11 PM.
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Old 11-22-19, 09:24 PM
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Found the manual. I was pouring oil in the wrong hole. Not sure what that hex screw with ball bearings and spring is for. The oil is added by removing the bleeding screw. I'll give it another try in the morning.

https://drive.google.com/file/d/1OSWXxhy-rFEsL10lBceQZX7XiMcUpoYF/view?usp=drivesdk

 
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Old 11-23-19, 03:46 AM
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The ball bearing is a check valve.
 
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Old 11-23-19, 09:56 AM
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The ball bearing is a check valve.
Okay. Thanks.

I removed the bleeding screw/oil fill plug and added a good amount of oil. I then performed the bleeding procedure outlined in the manual. The saddle raises and maintains pressure when I push the handle down, but as soon as I raise the handle, the saddle drops again. It's like a teeter-totter. I can stand on the saddle while holding the handle down and it supports my weight. Now what?

If I remember correctly, the saddle began to drop after raising the handle after I screwed around with the check valve (what I originally thought was the oil fill plug). I removed two metal balls and a tapered spring. I'm pretty sure I put them back in properly, but maybe not. Does the current operation sound like a check valve problem? Could I have screwed something up by removing the balls and spring and pouring oil into that hole? I suppose I could have screwed up the lower separator and ball (parts 8A and 7A in linked diagram). I didn't remove those, but pumping the handle with the upper parts (11A, 49A, 10A, and 9A) could have knocked 8A and 7A out of position I suppose.

http://www.mediafire.com/view/op58dx...Parts.jpg/file
 

Last edited by mossman; 11-23-19 at 10:31 AM.
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Old 12-01-19, 07:37 PM
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More info

The install of the check valve items needs to be redone. Here is a good jack repair guide, check the section " For the IDIOTS Who Already Messed With The Check Valves" . You are not the only one who has mixed up the oil fill hole with the valve body holes!

HYJACKS.COM/JACKS BASICS PAGE/H7.HTM
 
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