I recently bought an '89 Grand Prix with a 3.1. My problem is, it overheats. When it overheats it starts running rough and dies. If I feel the radiator, it's not even warm. I tried burping the system by letting the car idle in my driveway with the radiator cap off. I filled the radiator to the top and watched it. The coolant was bubbling and it dropped about two inches. I refilled it and it just sat there bubbling. I checked the temp gauge periodically and after about 15 minutes the car was starting to overheat and I shut it off. The radiator was cold and I stuck my finger in the coolant and it was cold. The thermostat housing was hot. I took off the water pump to replace it but it was nice and tight with no play and no visible damage. Before I did this I ran a water through the radiator with a hose and it came out both sides and the engine so I don't think the rad is plugged. Any ideas? I'd like to get this car going so I don't have to drive my gas guzzling '68 GP to work every day. Thanks, Jimmy.