How to fix leaky hydraulic press jack?

[ericc]

I bought a 12 ton hydraulic press at a garage sale that has a leaky jack. It is one of those unbranded Made in Taiwan ones with an orange frame. It looks like a Harbor Freight, but isn't. Anyway, it has a pump piston that leaks oil with every stroke of the handle, even with no load. I swapped the jack with an old Hein Warner 6 ton jack of the same size. Boy, what a difference in quality! It would be nice to repair the original jack, though. I pulled out the piston and it has an unusual arrangement (at least to me) of two hard washers at the end of the rod and an o-ring in the middle. The rod is 0.428" and the bore is 0.430". The o-ring is difficult to measure, but looks like about 0.422" in diameter, definitely smaller than the piston. The two harder washers at the end are 0.426". This looks a little bit off. They should be closer or even slightly larger than the bore size, right? I searched a bit online, and it said go to a hydraulic supply store and they should have replacements in stock. It seems that the only store in San Jose is Royal Brass, and they only do hoses. There are hydraulic service companies, but they don't appear to sell parts over the counter. From what I see on the Internet, the two hard washers at the end of the piston are a U-cup seal and a backer. I can find some of these on EBay, but they don't seem to quite match the size. Is this something a rural type of hardware store would have? You know, the legendary stores with all the little drawers in back.

 

[whitmore]

I bought a 12 ton hydraulic press at a garage sale that has a leaky jack. ...The o-ring is difficult to measure, but looks like about 0.422" in diameter,

Probably a metric hydraulic seal ring, and possibly unavailable locally.
This outfit https://www.theoringstore.com/store/index.php looks like a likely place, came up when I started down a similar path.

 

[chip maker]

You could just go to Harbor Freight and get a new jack for $35.00 and save alot of messing around. Sometimes penny wise dollar foulish.

 

[Alcap]

I’ve used Hercules Hydraulics a few times for odd , old and one off repairs . https://herculesus.com/?gclid=EAIaIQobChMIht2s1rL-8wIVSKiGCh2zeQNbEAAYASAAEgL44PD_BwE

 

[Eddyde]

I rebuilt a 1940's vintage hydraulic press and was able to find all the cup & piston seals etc at Mc Master Carr. It looks like they have a .437" cup seal that might work for you.

 

[AGCB97]

You could just go to Harbor Freight and get a new jack for $35.00 and save alot of messing around. Sometimes penny wise dollar foulish.

Or even upgrade to a 'air over hydraulic' one. Was a great improvement on mine.
Aaron

 

[ericc]

Great! Thanks for the replies. I found matches. That was easy!

So the fact that the current seals measured under the bore size is the reason for the leaks? It appears that the application is not that critical, and these should just work. Buying another jack is an option; the one at Harbor Freight fits. It will be instructive to fix this one, though. It is a small gamble, and I'll probably end up learning something. Besides, I have the Heim Werner 6 ton jack which runs the thing just fine. Thanks again; these replies really pointed the way unlike some of the other hits I got.