Overheating Problem

Radiator is the same for the V6 and GT, believe it or not. The only variations for our years are for Automatic (for the transmission cooler ) or manual transmissions. There's a lot of things that can cause the engine to overheat. And there are a lot of things that can make it look like the engine is overheating.

* The system should be sealed, and take 16lbs of pressure. If the system can't take that pressure, the temperature will rise faster than normal.
* The ECT (engine coolant temperature) sensor could be bad. It tells the car's computer the coolant temp, and if it fails the computer will run the engine hotter than normal.
* The CTS (coolant temperature sender) is only used for the gauge in the instrument cluster. If it's bad, it would only look like the engine is overheating.
* Your new thermostat could be bad, though unlikely.

My first check would be to buy or borrow one of the pricier code readers, one that can read PIDs. That feature will let you see the output of the ECT. Next, I would buy or rent a radiator pressure tester kit. As its name implies, it will let you test how much pressure your coolant system will take. If it can't take 16lbs of pressure, you'll find a leak. The leak will usually be a hose clamp that isn't tight enough or a pinhole leak in a hose.