Coolant Sensor Problem

I have a 1996 Jeep Grand Cherokee Limited with about 125000 miles. Coolant sensor bad was flashing for a day or two then it goes away. Coolant was good and no overheating nothing. Left for vacation and truck was fine, stopped at a rest stop and coolant everywhere. There was no sensor bad light, no overheating, no coolant level low, no check engine light, nothing just coolant all over. So I replaced the coolant sensor on the block and the thermostat and the water pump thinking that would be it, that is where it looked like it was leaking. Now I just found out that the truck had been overheating and cracked the block. I don't want this to happen again when I replace the block, any one know if the sensor will fix the problem or is it wiring? Any ideas on why all this happened at once or what caused the main problem?

Usually when the coolant sensor bad light comes on it is for the COOLANT LEVEL SENSOR in the reservoir. I had this problem and I replaced coolant level sensor and the Coolant temp sensor on the engine and still didn't get rid of the problem my problem was actually the plug on the back of the VIC - the when the connector gets soldered to the board in the VIC the solder joint was broke.