Possible coolant tank leak - or can something else cause it?

[patssle]

I have some coolant fluid on the bottom of my trunk. I figure the coolant tank is leaking but I can't find any cracks using flashlight and mirror. It only has 30k miles on it.

3 weeks ago the fluid level light came on and I added half a cup of water after pulling over then driving off. I didn't do any venting afterwards or anything (oops). Monday I get home and it gushes water underneath the right rear tire. So I figure it came out through the pressure valve due to my failure to properly add water and vent. Parked it until today and test drove...noticed condensation on the trunk lid then fluid on the trunk floor. But I can't find the source of the leak.

Also - does the coolant level sensor have a gasket or o-ring? I can't find one on the parts - can it leak?

Also I noticed the bleeder valve was up during operation and you could hear gurgling in the tank. Is that normal for it to be up even with the clip horizontal? I could push down on it and close it and the gurgling would stop.