i have a 2005 pt with overheating problems .

Judging from what others have been saying, your cooling fan for the radiator could be contributing to the problem. My own experience suggests something much more involved and costly. When my PT overheated driving around the city, I did the same as you...replaced the thermostat, which worked fine initially. But when I took my car on an interstate trip, I overheated three times within 450 miles. When I finally had it towed into a reputable shop, they informed me that my head gasket would need to be replaced along with the water pump. Since the car was almost to the 100k mark, I chose to have the timing belt replaced as this maintenance is recommended at this interval. I authorized the repairs and have had no recurrence of the problem. I hope your problem is much less expensive to fix. Just saw your question and thought I would offer feedback to give you a direction to begin your search.