My dart sat for 4 years and seeped for 4 years. Looked just like your photo when I found it and I pulled the carpet up there was pools of fluid in the recesses of the floor and the paint was goo. In my case the carpet was saturated with it as well.
But no smell, no feel, no nothing but fluid loss. It never got to low so no air in the lines. The reason I looked for it was the rear most reservoir was really low while the front was ok. I would add fluid and in a fairly short time it would do it again.