I will tell you my symptoms and let you alll decide if this is the reason for a new stat. I start my car up and leave it running between 30-45mins and then drive. The car temp is at 200-215*/ Once I statrt driving for a while like maybe 5min, the temp drops. It will go down to 150-165*. The heater is on 90* and on high and will suddenly blow cool air while the car temp drops. So, is this the common sign for a bad t-stat?

Don't you think that leaving the car on for 30 minutes is too much?
I've heard that it'* a bad thing. But I don't actually know that if that'* the reason why you have a problem.

I'm very sorry though.

It'* staying open too long, or it'* a very cold Tstat, letting too much coolant flow and cool.

30-45 min of idling is very bad for your car. I would suggest a much shorter time.

Nope, I leave it running like that so I won't have to sit in a cold car. I only had the car for a month now. I am doing some major work on her, thats all. But i need to know if this is the t-stat or something else.

It'* the Tstat, but you'll be making more problems down the road if you let it idle that long.

EXACTLY!!!!!!!!
Stop doing that! Just 10 minutes is more than enough!

Can you all tell me what problems are in the long run then?

You only want to let the car idle enough to get the engine temp up to about 140. Driving it will heat it up faster then idling. Prolonged idling will cause carbon buildup on pistons leading to higher compression and thus more prone to detonation. Also you may be running to long in a rich condition which possibly could foul out the 02 sensor much faster.

ok, thanx. I just put that o2 sensor in yesterday. dont want to get another one no time soon either

The o2 should be fine if everything else works right correct? Ive had many people say that fuel injection can idle forever with no problems because its always calculating the best combustion ratio for the air speed / engine speed / air temp.

Anyway if you idle that long then you can just do the "italian break-in" aka. flooring it to clean out the carbon with some high revving.

The name came from italian made cars that need high engine speed to warm up and keep cleaned out because of the way the engine was designed. Or something i cant recall 100%

~Got a lot of information from Click and Clack... they are mechanics that write articles in the paper.