high idle?

now to day i took car car for a drive and it still has that high idle. the temp. of the car was up high again. so i open the hood i heaar a hissing sound and i get flashlight and look and see coolant coming out of the radiator in a little hole. is their any other sensors besided the temp sensor in the car? casue the hole is just after the tube with the temp sensor and it could be cloged casue it is pusing out hard to be hearing it hissing. could it be a clog and posibly another sensor telling car to run faster to get the anti-freeze pumped into the engine to cool it down? 91 sunbird le 2.0L TBI OHC