Hydraulic Cylinder problem High Transission Jack

[widetrackman]

I bought a used NAPA high transmission jack model #520-4002. It has a slow leak down, about a inch in 3 minutes with a 60 lb load. The only visual fluid leak is at the release valve. It does not look like much fluid is coming out but I can not tell how much as it goes under the base into the housing support. I removed the release valve and polished the seating part. I then put Dykem on it, screwed it in until it seated. Backed it off and seated firmly several times. I then removed the valve. It showed a 100 % contact.. Still leaks down with seepage around the threads. I researched the jack and found the cylinder is the same as a Sunex or is a Sunex. I would like to fix the cylinder I have in stead of buying a new one at $69 as a new jack from Summit (same at NAPA) for $144 shipped) I would be willing to pay $40-50 for a new ram. I can find lots of 4 ton rams in that price range but none have a flat base with 4 bolt holes. Sorry for being so lengthly. Thanks

 

[widetrackman]

I have been thinking about the leakage, the release needle showed 100% seating. Maybe the seat is cracked. Are the seats made into the casting or replaceable. This thing is a pain the ****, leaks just enough to annoy if someone is helping you but not enough to replace ram. Any ideas on how to fix or repair. Thanks

 

[gungatim]

I have been thinking about the leakage, the release needle showed 100% seating. Maybe the seat is cracked. Are the seats made into the casting or replaceable. This thing is a pain the ****, leaks just enough to annoy if someone is helping you but not enough to replace ram. Any ideas on how to fix or repair. Thanks

have you read through Highball's floor jack rebuild thread? lots of good info in there that is likely (in theory) applicable to your cylinder...maybe he'll chime in.

 

[widetrackman]

I searched around and could not find anything about a slow leak down when release valve shows a good seat but leaks oil out around the threads. BTW the o ring seal is very tight so one would think this is a pressure leak. The only thing I can think is the seat in the base has a crack. If that's the case what can you do? are they replaceable? One other thought should there be a ball in there that previous owner lost ?

 

[gungatim]

well that napa jacke is made by sunex, the rebuild seal kit RS5040BSK is readily available, so maybe the seal is just bad in the release valve. but before I did anything else, I would PM Hiball directly or post on his thread.

http://www.garagejournal.com/forum/showthread.php?t=51105\