ncarring

Some time ago I inherited a second trolley jack from my Dad, but it was in a bit of a sorry state. The pump piston was seized, from where the jack had sat outside for a long time. Last weekend, I finally managed to free it, after soaking it in WD40 for some considerable time. However on unseizing the pump piston, it came right out, and revealed some very black and dodgy looking oil underneath. I decided to replace it for safety's sake, and this is how:

1. Visit your friendly motor store, and buy some jack oil (not brake fluid, not power steering fluid, but jack oil).
2. Remove the cover plate off the top of the jack.
3. Find the oil filler in your jack. On both of my budget trolley jacks, this takes the form of a rubber plug in the top of the cylinder. Posher jacks may have a screw filler. If your jack has a screw under a rubber cover labelled "do not adjust", leave it alone. This isn't the filler.
4. Remove the filler cap, and also remove the release valve completely from the jack body. Be careful, there may be a ball bearing in the bottom acting as the seal.
5. Up-end the jack, and let the fluid drain out from the release valve hole. Drain into a suitable container and dispose of it responsibly afterwards. Occasionally put the jack back on a level surface and pump the handle very gently a couple of times, to move the fluid around. Repeat until no more fluid drains out.
6. Clean the release valve and replace it, but do not tighten fully.
7. Now you have to decide how much oil to fill the jack with. Properly, you would measure the fluid you removed, and replace with the same quantity, or slightly more, to allow for leaks and evaporation. However if you haven't measured it, the following method works well:

a. Put some oil in through the filler, just a little - the container should have a long neck to help this process, but a little funnel may be required.
b. With the release valve still not tightened, pump a few times to distribute the oil. You will hear bubbling initially, but it should stop. You don't need to replace the filler plug during this part of the process, or the next step.
c. Tighten the release valve, and pump up the jack. It will probably not pump up to its full height initially. After a few pumps, it will stop lifting, and you will hear bubbling again. Loosen the release valve and let the jack retract.

Repeat a-c until the jack pumps up to its full height. My jack took around 100-125ml of oil. Quantity will depend on the make and capacity of the jack.

8. Replace the filler plug, and clean up any oil dribbles. Your jack is now ready for use again. Take this opportunity to oil all its pivots with some engine oil or similar, and give it a clean.

That should last you for a few more years.

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Nick

North Wiltshire RoADAR

Basil

If you can't find proper jack oil for love or money - is there any reasonable alternative? eg caterpillar hydraulic piston oil?

nice to know about this - one of my jacks is a bit dodgy - good thing I always use jackstands....

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