Accent LC (2000-05) :: Vehicle Overheating In 60 Degree Weather

2005 Accent Hatchback... As of Friday I noticed my vehicle had been overheating. The coolant levels haven't seemed to change but this is a recent issue so there still may be a slow leak I'm not noticing.

I let the car idle to normal operating temperatures over the course of 17 minutes. While warming up the top radiator hose became warmer, and eventually hot -- the bottom hosed seemed to stay cold and didn't appear to change in temperature.

After reaching normal temps I let the car sit another 3-5 minutes to watch the temp gauge, which did not move. I drove the vehicle stop-and-go 5 laps around my complex(about a mile). There was no noticeable change in temps.

I then turned on the AC which blew ice cold and did another lap. After the first lap the gauge began to rise fairly quick. I immediately turned the AC off and drove the rest of the 2nd lap. The temperatures continued to rise throughout the 2nd lap. I parked with the gauge at about 62% assuming normal temps to be 50% (middle of gauge).

Once parked I checked the hoses. Top hose was hot, bottom hose cold. Coolant tank was at the HIGH mark previous to it being on the LOW mark before the car was started. The oil is at the same level as it was when I changed it a couple months ago, and it looked clean.

Before I started the car I also noted that the radiator was filled to the top. As mentioned OIL looks clean, coolant looks clean. No unusual smoke coming from exhaust or engine.

I've done a lot of reading and some information suggest that the thermostat might be stuck closed. Other post say that if the thermostat was stuck closed the top hose wouldn't get hot. But, these are also post for other vehicles so that might vary here.