Where is this oil coming from?

I was unloading a truck when I noticed some liquid on the right side fork. To find out what it was (could only be water or oil) I dipped my finger in it and the rubbing test revealed it was oil.

The forklift just went through maintenance the day before, which meant all the hydraulic connectors were checked as well. Not uncommon for a drop of oil to be found afterwards, especially since there are a lot of hydraulic systems in the main beam.

I cleaned it up and continued unloading. A minute later another drop was there.
We started wondering if any of the hydraulic connections might be leak. Maybe the moment I use a certain system another drop was squeezed out.

To find out what was happening we cleaned it up again and went through all operations. Ah, there's the drop of oil again.

But noone saw which connection squeezed it out.

Then someone remarked: "The fork is bleeding" and we payed more attention to the spot itself instead of the hydraulic connections.

Indeed, even at stand still the oil was somehow coming directly out of the fork's top backside.

It was cleared up the next day, when the maintenance guy was called back to check it out.

Turns out, there is an hydraulic system running through the fork itself. This allows us to extend it from 1.2 meters to 2 meters for longer loads. Of course we knew about the function but were astonished to hear that instead of connecting the hydraulics with a tube, the inside of the fork's backside is actually used.

After being in use for about 8 years now enough microfractures finally built up for this oil leakage.