GU Coolant Reservoir Tank

[GUtsy ute]

Can someone please tell me what is meant to be on the opening on the neck of the
filler spout under the yellow cap.
Thanks.
http://i994.photobucket.com/albums/af61/GUtsyute/canopymount004.jpg

[snakessou]

I think another water tank (the overflow tank). At least thats whats on mine.

[megatexture]

mine comes from the main tank like that then flows into the bottom of a smaller one but mines a crd so looks a bit diffrent is it spitting out ?