Need help with 2013 Volvo d11

Wich line? More then likely its one of the fitting that is leaking. Get some soapy water and track it down.

 

It’s a quick connector. If you can get the rubber oring (when they age, they get stone hard and start leaking air), you can pop the line and replace just that. If you don’t have orings, just get the new L shapped fitting at Volvo.
Doesn’f natter where is it going, those quick connectors all start leaking at some point.

 

In the picture it’s an air governor.
If you’re asking what’s on the other end... well, just trace it down and post a pic.

 

Hey, I looked at mine, and that hose goes just one feet down to an engine fan activator.

 

Black is for fan clutch yellow is governor supply from wet tank