That's not to say that your thermostat isn't ruined by now. Try this. After you replace the thermostat, which is located under the thermostat housing here;
http://repairguide.autozone.com/znetrgs/
http://repairguide.autozone.com/znetrgs/
http://repairguide.autozone.com/znetrgs/
try bleeding out any air through the air bleed, located in the thermostat housing. On the right in the first picture.How do you change the thermostat in a 97 Dodge Intrepid?Remove the hose connection where the upper hose meets the engine block. The thermostat is located there and will just lift out for replacement.How do you change the thermostat in a 97 Dodge Intrepid?could also be the heater coreHow do you change the thermostat in a 97 Dodge Intrepid?the cooling system in this type of car needs to be bled out, sounds like you are already having issues with the system having air pockets in it. so when you go and buy your stat the person at the parts counter will have the proper procedure to bleed the system, you didn't give the reasons for this issue but if its just the stat if you don't bleed the system you will have the same issues that you are dealing with now