2002 Chevy S-10 2002 s10 Over heating!!

I was driving on a local road by my dorm in VT and I noticed that it smelt like anit-freeze I looked at the guage and the temp. was rising I promptly pulled into a cleer parking lot and parked over some clean snow, I observed that antifreeze had been released out of the over follow tube by the front right wheel housing. The rest of the engine was sound I checked the belts, checked for any other leaks and drips nothing. I am most confused and so is my father who is a mechanic(turbines) BUt also a hard core chevy guy and nows his stuff! But mostly confused becuase I had prior 2 weeks before changed the thermo stat when this similar thing happened, I also did a dex-cool change and checked everything to my ability!
This morning I changed the thermostat again and it didnt help it will get hotter than what ever in only aboput 10 minutes of idle/drive.