I can't get the search to work...does anybody have the thread with the link for filling up floor jacks saved. It was some companies web site that rebuilds them I believe...showed the best way to position them and which plug to use ect.

thanks

I would be interested in knowing this also. I have one that slowly lowers.

This one?
http://www.pirate4x4.com/forum/showthread.php?t=319504

yep this is the one right here:

http://www.hyjacks.com/H7.HTM

thanks

I was given a nice new floor jack awhile ago. The problem is it will only lift @300 lbs. It was a returned unit at a store and bought off the clearance rack. I suspect that they "tinkered" with the check / overload valve while tring to bleed the unit. There was screwdriver marks on both. The checkball and spring were in there. Are there any procedures for adjusting the settings on these? Is there a rule of thumb for turns out from the seated position. Which direction should I turn for more or less lifting preasure. It reaches about 300# and it bypasses preasure.
Its a standard chinese 2 1/2 ton jack. Its not the 80 dolar jack the next step up models that are out there. I can take a picture of the unit.

I would be interested in knowing this also. I have one that slowly lowers.

This could be a number of things. There could be a problem with the check ball not seating properly, or getting jammed with the spring. It could be a bad pump seal, or a bad ram cup/seal. If it were low on fluid, after a few pumps it would start to go up at a slower rate, and you'd feel air pumping into the chamber. What you are describing sounds more like an internal fluid leak or flow where it is not supposed ot be flowing.



I was given a nice new floor jack awhile ago. The problem is it will only lift @300 lbs. It was a returned unit at a store and bought off the clearance rack. I suspect that they "tinkered" with the check / overload valve while tring to bleed the unit. There was screwdriver marks on both. The checkball and spring were in there. Are there any procedures for adjusting the settings on these? Is there a rule of thumb for turns out from the seated position. Which direction should I turn for more or less lifting preasure. It reaches about 300# and it bypasses preasure.
Its a standard chinese 2 1/2 ton jack. Its not the 80 dolar jack the next step up models that are out there. I can take a picture of the unit.

I haven't rebuilt many Chinese jacks (we generally turned them down at work) but I rebuilt just about everything else. Most jacks opperate almost in the same fashion from brand to brand. Usually, one of those screws will hold two check balls, and two springs under a rubber cup, with the screw on top of it. These are your check balls, and need not be messed with.

In the other one, if you remove the screw there is generally another screw beneath it. This one adjusts the pressure the jack will exert. It is likely if the jack was opened up, they unknowingly pulled this screw out, which would be why it will only lift 300 lbs now. Generally turning it clockwise will increase the pressure, but some jacks have left hand threads. Basically you want that screw to move down into the jack body to increase pressure. You want to be carefull with how much you tighten this though. Do it in small steps and test it, because you can overload the jack and destroy the seals. Its possible to turn a 2 ton jack up to 3 tons, and rip it all apart internally. So if you have a way to measure its pressure output at which point it clicks off and won't lift anymore, thats the best way to go about it. Hope this helps.

I replaced the main shaft seals in my 26yr old Sears floor jack.I refilled the cylinder by removing the top cap with the cyl. vertical.Just poured the oil to the top.

Thank you for your response, I will check it out.