[Latitude 28]

I'm not positive of the source, but I'm getting leaking over the top area of my hydraulic tank.  So, I'm starting with the Cap.  I can't find the vendor/part info.

This is the tank:


And here is a closeup of the cap:


Hopefully, someone has some info on it for a 2015 class coach.

I've tied paper towels around the site-glass and get a bit of oil out the vent hole...wouldn't think this is normal and hasn't been a problem before.

Steve,
Here is an assembly from McMaster Carr....https://www.mcmaster.com/products/hydraulic-tank-caps/ that looks like your cap.