I was inspecting how to get the rear caliper off when I noticed this green metal hose by the rear axle. It's on the opposite side of the exhaust, situated in between the left halfshaft (if looking from the rear) and the bottom of the spare wheel recess. Covering the end of it is a rubber hose with a white plastic cap at the end. This cap has holes/vents on its sides just like a hubcap.

This rubber covering with the cap is nearly falling off the hose. I've taped it together but I don't think it'll last long. What is this hose and should I get a replacement rubber/plastic end or whatever it's called?

Thanks

Aslan