I have a 02 Monte Carlo and having problem with the temperature . When in park the temperature goes up but when I start to drive it ...it start to fall and little heat is coming out. It takes me to drive it for awhile for it to stay up . But only do this when the temperature in the low 30s and 20s.Please help I'm freezing going to work in the morning....here in Indiana

 

To me it sounds like you don't have a thermostat in your car. That won't really hurt anything in the summer, but in the winter time, you need one. I would first check to make sure that one is installed. If not, put one in. Another problem could be that your thermostat failed in the open position. Same fix. Just replace the broken one with a new one. They are very cheap and easy to do. Good luck!

 

Sounds to me like a stuck thermostat...

Especially in colder tempatures.../ Its stuck closed or clogged..whens the last time you did and cooling system maintenance?
You may even have a faulty/ bad water pump.. Or something as simple as a bad radiator cap!

Whens the last time you checked the radiator fluid...????

 

Sounds to me like there could be air in the cooling system. Get it flushed and change the thermostat

 

I had to replaced thermostat last winter but maybe its gone bad again.Yes I check the fluid and it was ok had to put alil in but it was top off. But the air in the coolin system that I need to check. Hope that is the problem ...going to check that and I update you guys let you know how that work out. Thanks 4 the info it real helps

 

I agree with making sure the system is full (no air pockets) and that the thermostat isn't malfunctioning, but when ambient temperature gets <20° what you are describing could be considered 'normal'.