Overheating

Now that it is getting colder, I used my heater for the first time and noticed that my Temp gauge raised up to the redline---before anything major happened I turned the heater off. I find this really strange because during the summer I used my A/C and I had no Overheating problems. Any suggestions? :banghead:

mrurban, you might have a leak in you're heater core and lost almost all your coolant out of the leak! you'de probably have noticed the coolant on the floor board and the strong sweet coolant smell as well unless you're using straight water which wouldn't be good either! the only other thing i can think of and it is a stretch is that possibly when you turned on your heater the core might have temporarily cooled your water while acting as a second radiator as heater cores usually do and this caused your main coolant thermostat to close and then it got stuck shut and won't open now casing your overheating! might want to remove and check your thermostat by puting it in a pot of boiling water and seeing if it opens up or not then replace if necessary. good luck!