Ac port, is there a washer or o ring under here?

[owas]

So the w140 air con decided to start leaking, just when I need it

Tracked it down to this port, not the valve itself but if you put a rag over where its screwed into the fitting it stops the gas hissing,

Is there usually an o ring or washer under here? I can't remove it yet as it's a slow leak and it's still working so I'm waiting for it to go empty.

 

[voipio]

If it's hissing, it'll be empty soon!

There will be an o-ring seal between the port and the part it is screwed to. Not all vehicles have ports that are screwed on. Some are alu soldered in place.