Chrysler Repair: engine cooling system, chrysler sebring, engine cooling system

Question
I have a 2001 chrysler sebring lx.  Not sure on the engine size. I was driving home from work and my temperature gauge went all the way to the top,warning light came on to. No steam was coming from the engine,but my gauge said it was hot.  Got home checked the reservior and there was still water in there, just not filled up all the way.  So I put water into it along with the radiator.  Radiator was pretty dry. Four days later I notice my heater isn't getting hot,so I checked the overflow bottle and it is very low,so once again I put water in it and the radiator,heater is hot again. I checked for leaking water,but haven't seen any. The fan is coming on.  I was really hoping that it is just the thermostat.  Any suggestions would be helpful.

Answer
I would say that you most definatly have a leak.The only real good way to be sure is to put a pressure tester on it.If you had a bad t-stat,you would be over heating all of the time or you wouldn't have heat all the time depending on which way it failed.The water pump on both engines available in this car is not very visible.Did you buy a service contract with the car?Could be covered if so.Best thing to do is have the system pressure tested.