Trolley (floor) Jacks

Never ever get under a vehicle on jack only. place stands under the vehicle when up in position.
As said they generaly allways leak from the pump piston seal, not a safty issue.
But if it is leaking from the ram seal or lock off valve this could be a saftey issue, they just tend to sag slowly this is why you should use stands as well.

HA-Id suggest that anyone who gets under a car on a jack leaking or not is likely to fall victim to Natural Selection.

Dont do it DIO.

It will probably go back to China as scrap & come back as something else to haunt you!!!!!

such as a Great Wall ute!

I just bought another Jack but thought I should fix the old one as well (same as yours I imagine)
So anyway remove the jacking pump thats pretty easy just split pins, and pull the piston or plunger out! then you need to remove the old seal inside the bore the plunger goes in to. Thats easy then find another O' ring seal there pretty close to the clip on Garden hose fitting size! so if you have a 3 dollar plastic box full of various size seals there will be on inside fairly close.

Buuuut I found you can put two seals in one on top of the other then it might last longer. Then fill with SAE 20 oil or ATF through the little round rubber plug you prise that of with a screw driver blade and fill with approx 150ml of oil or nearly to the top of the filler plug.

Then you have to pump bleed pump bleed (bleed through rubber plug filler! And if it don't work you might need to remove the red plastic plug that say's do not adjust and screw that half a turn at a time until it pumps correctly. It's a bit of a pain but can be done. All the same mine seems perfect now but never ever trust a jack as said before! crush injuries will kill you after the weight has been removed if you have been there for some time.

Always use stands or good hard wood flat blocks to suport the vehicle when underneath.

Just watch out for the little ball bearing that's under the plunger, It won't come out by it self but will ! when you turn it up side down to drain the old oil out. Cheers.