Sunday, July 31, 2011

Hydraulic Bottle Jack Filling and Release Valve 'Repair'

The jack pictured below was a roadside find.

It appeared to be in pretty good condition -- no signs of having been abused, or even of having ever seen much use. Its ram would raise a bit, but it wouldn't support any load. I set it aside and it languished for months on a shelf, until I finally picked up a bottle of jack oil at Canadian Tire. I figured that even if it's full, once I start looking into its works it'll likely lose some oil, so no point in proceeding without oil on hand.

When I returned to the jack, its ram wouldn't raise at all anymore.

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These jacks all have a fill plug on the side of the reservoir jacket somewhere. Here's a close-up of this one's.

It's just a resilient plug that can be pried out with a screwdriver. Here's the jack again with the plug removed, and the oil I bought for it. The jack appears to be completely empty. They're supposed to be filled up to the bottom of the fill hole.

On the oil bottle, note the red stripe at about the middle where it says "ISO AW32"[1]. It seems that "ISO AW32" is the key specification for hydraulic jack oil. Whatever brand you get from wherever you get it, if it complies with ISO AW32, it's the right stuff.

It looked to me like this could get messy, so I arranged to do the filling on my oil change drain pan. The only funnel I had that was near small enough was my Coleman camp stove fuel funnel. I took out the funnel's filter element for this.

That almost worked. But the funnel's spout proved to be too snug a fit in the fill opening, so the spout was unable to vent[2]. I solved that with a one-inch length of 1/4' diameter thin-walled brass tubing. The tubing was a nice fit in the end of the spout.

I filled the jack full, then set it upright and let the excess empty. I tried the jack and I was back to where I'd started -- the ram would raise, but it wouldn't support a load.

I tried a procedure known as 'priming'[3]. To 'prime' a jack, you close the release valve, manually raise the ram to its full height, open the release valve and push the ram back down. That had no effect.

The jack was behaving exactly as if its release valve weren't closing fully. I unscrewed the valve stem completely and took a peek inside -- there was no check ball in there, and it sure looked as though there ought to be one. Here's a shot of the valve stem, along with a 1/4" diameter ball bearing I got from my stash of bicycle parts.

Note the dimple in the end of the valve stem. That's a pretty certain clue that it had been operating with a ball under it at one time.

I reassembled the valve with the ball inside and the jack worked.

Here it is under a Ford Ranger behaving like a jack.

So, for the price of a bottle of oil and one ball bearing from the bike shop, I've got a working jack. Not a bad outcome at all.

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Storing a Jack

An idle jack should be put away with its ram fully collapsed, so it's protected from rusting, and its release valve closed, so it can't leak.

The 'seal' around this jack's release valve stem is only as effective as it needs to be, which is to say 'not very'. If left unclosed, the release valve will leak oil. That's no doubt how this jack came to be empty -- with the release valve's check ball missing, oil had a slow leakage path out past the marginal seal.

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Notes:

[1] 'ISO' stands for 'International Organization for Standardization', which has a rather Orwellian ring to it, don't you think? (And they seem to be a bit 'letter-order' challenged.) I'm led to believe that the 'AW' stands for 'All Weather'. The '32' is an ISO viscosity number.

[2] Nothing is ever as simple as it looks like it ought to be.

When a funnel's spout is a snug fit in a vessel's only opening, the air inside the vessel can't escape as liquid is poured in. Liquid fills the funnel's spout and backs up into the funnel.

Some funnels have a self-venting feature.

Note the ribs on the smaller funnel at the left in the above photo. The ribs prevent the spout from 'seating' in an opening, and so maintain a venting path. The smooth spout on the larger funnel will happily seat snugly and provide no vent.

A solution is to drape a little piece of telephone cabling wire over the neck of the jug, or whatever, that is being filled, so the spout doesn't seat.

Just about anything will serve -- a bit of plant stem or leaf, anything that will displace the spout a little so there's an air path out to the atmosphere.

[3] What priming allegedly does is it draws oil from the reservoir through two check valves and their passageways, presumably purging any air that might be interfering with the hydraulics' works. I'm not sure I understand that, but that's what priming allegedly does. Anyway, there's a pretty good animation of a jack's operation here.

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1 comment:

  1. Thanks for this. First search result on DuckDuckGo and exactly the answer I needed. Manual hydraulic ram I couldn't figure out how to fill. Disaster averted!

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