[kaptain]

Thanks to Richard and all who shared useful information in this thread.
I discovered I have a hydraulic leak at the fan motor too. Initially, it looked like a coolant leak because the leaked fluid was red, the same color as the coolant, and the coolant tank is on top of that fan. A tip from Richard responding to my post convinced me it's a hydraulic leak.

I first cleaned that area and returned the next day and saw leaked fluid there again. Now it's clear to me it came from the gap of a hex screw or Allen socket screw.
According to the manufacturer of this OverHung Load Adapter, Zero-Max, this socket screw has 1/4-18 thread, but no documentation showing how long this screw is, and overtightening it could result in the screw touching or blocking the bearing of the adapter.

I was considering replacing this screw today, but I realize removing this hex screw will result in some mess due to a lack of a valve to shut down the drain of hydraulic fluid. So on the 2nd thought, I'll order a set of Hex Head Pipe Plug Fittings (which contains 1/4 size, and I hope the thread matches).
https://www.amazon.com/gp/product/B095YCY85S/

I was hoping to find some plugs with an o-ring and a larger head to achieve a tighter seal, but I didn't find any.
I will provide an update with the final results later.

Leak Found
   

Leak Fluid Cleaned
   

I came back the next day and saw the same leak again. Now it's clear the leak came from the edge of the hex screw on top of the Overhung Load Adapter.
       

Cleaned again and sing a 6mm (better with 1/4) hex wrench to tighten this screw.

   
Replacement plugs ordered
   

Zero-Max made Overhung Load Adapter specifications.

L600130-OCR.pdf Size: 25.88 KB  Downloads: 11