Hydraulics

I need to repair my floor jack, therefore must buy some hydraulic fluid and o-rings. I know from past experience that not all o-rings and fluids are equal, but have not been able to find any specifications for my particular jack. I sent some emails to some suppliers asking about this, but thus far have received no replies.

How does one determine exactly which o-rings and fluid to get? I'm only referring to materials and forumula.

Okay, thanks. I was going to order them online, but since I'm only a couple of blocks from Autozone, I guess there is no excuse for not going there. Am I to understand that automotive fluids and o-rings are the same as used in hydraulic jacks?

EDIT: Forget the part of the question about the fluid, because I now see that it is specifically jack oil. I thought it curious that while AutoZone is cheaper than what I found online for the fluid, the same isn't true of the o-rings, as can be seen by comparing the links below:

http://www.autozone.com/autozone/acc...ier=76119_0_0_

http://cgi.ebay.com/ebaymotors/?cmd=...K%3AMEWAX%3AIT

You're probably right, but without actually tearing into the jack, I'm guessing that there are only 3 o-rings involved...1 on the release valve, one on the compression piston and 1 on the output shaft. Does that sound right? Not having the jack apart, I can only guess which seal is bad, because there is no sign of external leakage, only that it doesn't hold pressure.

The pump and cylinder are most likely NOT O-rings. O-rings are not meant to hold high pressure. These will be lipped seals. If there's no external leak, the problem is, more likely than not, just a check ball that's not seating. A way to try and clear dirt from the ball and seat is as follows.

1. Make sure the jack has fluid.
2. Open the release valve.
3. Lift or pull the cylinder up by hand. Let it go down. Repeat this 2-3 times.
4. Close the release valve and see if it will pump.

If it pumps up, I suggest doing the following:
1. Drain the fluid.
2. Fill with Stoddard Solvent (Paint Thinner).
3. Repeat step 2 & 3 above except 4-5 times.
4. Drain the solvent and refill with Jack Oil.

You should be good to go.

I've got more floor jacks and bottle jacks in the shop than I know what to do with. All but two came from the salvage yard. They end up in the scrap yard for all the same reason--They don't pump up. I do the quick test and nine times out of ten, they start working. I then buy them for $0.15/lb. (Earlier ones were ten cents a pound.) If there's no sign of leaking, a re-seal is a waste of money. A good cleaning will get them to work again. It's common for paint chips from the fill plug, dirt or bits of rust to get under the intake check ball. Give it try. It costs nothing.

carwiz said:

The pump and cylinder are most likely NOT O-rings. O-rings are not meant to hold high pressure. These will be lipped seals. If there's no external leak, the problem is, more likely than not, just a check ball that's not seating. A way to try and clear dirt from the ball and seat is as follows.

1. Make sure the jack has fluid.
2. Open the release valve.
3. Lift or pull the cylinder up by hand. Let it go down. Repeat this 2-3 times.
4. Close the release valve and see if it will pump.

If it pumps up, I suggest doing the following:
1. Drain the fluid.
2. Fill with Stoddard Solvent (Paint Thinner).
3. Repeat step 2 & 3 above except 4-5 times.
4. Drain the solvent and refill with Jack Oil.

You should be good to go.

I will give that a try, but since it already does pump up, but will not hold sufficient pressure to raise my vehicle, I will have to check it under load.

Just in case that doesn't work, if you are right about the internal seals not being o-rings, I'm wondering if they are user replaceable and where I would find those lipped seals?