How hard is it to rebuild a jack?
Do I need anything special like a press?
I will explain what I know below.
There are special tools the experts have and use, but I really have no special tools, primarily those described below!
The
first rule is, Do not attempt to rebuild cheapie import jacks they are not worth the effort.
The
second rule is find a good re builder candidate, the most common quality names in jacks that you are likely to encounter will be Blackhawk, Hein Warner, Walker I am sure I missed one or two, but these are what I am familiar with.
The
third rule is never spend more than $15.00-$20.00. In fact I always try to buy for ten or less cause it is really scrap you are buying on any crapped out jack, regardless the brand. You must look at every one as a roll of the dice, by the time you buy a kit and tear the jack down so you have the bottle on the bench you will likely have another $20.00-$40.00 in it keeping in mind you are not guaranteed success.
Rule four is always attempt to find the original tag listing all the specs like tonnage and most important of all, the brand, serial & possibly model numbers before you jump at the chance to buy a junker. If you do not have this info up front, you may play hell getting it once you have already invested money in it. (which is another good reason to stick to the mentioned brands, in the absence of the manuf. tag I would likely still take a chance on it, but that is just me.)
Rule five make sure you have a vise that is substantial enough to hold a drained bottle, the bigger the better! Also do not clamp a bottle into the vise by the outer skin or hydraulic reservoir, because you will likely have to put some hefty effort into removing the big hex nut at the top of the bottle that keeps everything tied together on the ram end obviously risking damage to the outer skin when really cranking down.
Rule six is do not waste your time attempting to rebuild a jack that has had the hardware that you use to raise/lower the jack twisted off in the body of the jack or other such extreme damage. Anything like that is beyond the tooling or capabilities I have at my disposal.
Rule seven once you have figured out how to get the jack drained & in the vise you need to get after either the big nut I spoke of in rule five (if you are lucky) or if you are not lucky you will have a essentially a big nut that is not hex shaped but rather is supposed to require the use of a spanner wrench to remove it. I have no spanners so I use whatever tool at my disposal will remove it; which usually ends up being a cold chisel, old screwdrivers I keep for such purposes, drifts, or other tools that I can fit in the slot and beat on. If you are lucky and get a big hex nut on top. A big pipe wrench, or a 3/4" socket of the proper size will usually do the trick.
Rule eight avoid using a torch for anything involved with rebuilding a jack. No one told me this, just my rule. I do not want to take the temper out of any parts so I always try to work it cold.
Rule nine take your time, if you get pissed it is time to go watch TV with the Mrs, come back later and have another go at it. I do not usually find penetrating lube to be a whole lot of good, but if you want you might try it during tear down.
Rule ten is once you are trying to clean things up and install the proper kit cleanliness of any components related to the inside of the jack is a must. Moisture and dirt/rust of any kind will kill a jack in short order so keep things surgically clean during re assembly. Also keep all your o rings, gland packing and the like soaking in hydraulic jack oil as you begin rebuilding, install everything wet.
No more rules, just additional tips. After tear down and before reassembly blow compressed air through all the passages; make damned sure you removed any steel ball bearings, needles or the like before blowing passages clear look real good, sometimes they are easy to miss. Once you have reassembled everything fill the bottle with fluid and try to make it work. I really do not know what to tell you about bleeding the jack of air after the rebuild, I simply fiddle around with the plug and controls until it begins working proper. I never really know how successful I have been until I reassemble the whole jack and actually lift a vehicle with it. BTW if your luck is like mine at some point when filling the jack with oil and trying to get it to function properly I always get a messy and uncomfortable shower of jack oil so remember during the bleeding of air to be careful because you are under pressure!
I have had very good success rebuilding quite a few jacks using the above method and ideas. I cannot begin to describe how much enjoyment I get out of resurrecting scrap to a usable tool. They really look like brand new if you go the extra mile and clean them up and give them a fresh heavy brush paint job and grease the wheels while you are at it!
Sorry this was so windy but I had to tell you everything about rebuilding one. I hope you find an old timer and give it a try!
2 ton floor jack for some time now,say the past 4 years. 
