Well, The bad news is with 3.5, they have head gasket issues when they get really hot.
IF it will go to hot regardless, I would suggest to see if the water pump works One way to test, is when it is warmed up, turn the heater on, and if the air is hot, and i mean hot not warm, then its still movin water. And which in that case, you may get away with a temp sensor.
But. Water Pump requires the front of engine to be taken apart, (timing cover, crank pulley.) It is also recommended that you have the timing belt changed to along with the tensionor. This job isnt cheap for havening a shop do it.
Last edited by EagleESI; 06-14-2007 at 03:54 PM.