Hi, I have a 2004 Colorado LS 3.5L with 80,000 miles. Its been overheating lately. I changed out the thermostat and it didn't help. The water pump seems fine and heat comes out in the cabin if the heater is turned on. The bearings are also ok and no leaks anywhere. I also burped the cooling system. Anyone have any ideas I can try? Thanks for your help in advance!