I have a 03 GP GT and I am having overheating issues. It has done this in the past and changing the tstat usually work. this time changing the tstat did not help. Any suggestions on how to fix this? I had an old guy tell me that I need to have my system flushed and it should fix this problem. I have never had the syatem flushed since I have owned the car (5yrs) It is my dd so it needs fixed soon. Please help???