Small Hydraulic Fluid Leak

[rScotty]

Yes, that's the cover #21;

That's good. Then I wouldn't worry about it. Put a diaper on it or a pan under.

Someday when you are changing out the hydraulic oils and just want to add a small project, get a buddy who is experienced with sealers to help you seal it properly.
I would NOT use any stop leak or such products. I would not loosen the fastening bolts.

If you want to clean around the outer edge of #21 and try to apply a sealer externally, go for it. I doubt it will do anything, but it will do no harm.