2001 Mazda Protoge overheating

[eagle6413]

my wifes car (2001 2.0L Protoge) overheated tonight. I got it home after letting it cool down for a while. The reserve tank was low when I first got to where the wife left it so I topped it off but the radiator was full to the rim. It ran in the normal range for most of the way home but started to spike just before I got it home. Also ran the heater full blast the whole way home just as a precaution but it never got warm. The reserve tank was overflowing (a little) at this point. After letting it cool I tried taking the cap off the radiator but couldn't tell whether the anti-freeze was flowing or not. Other than the typical antifreeze smell (not overly strong though) I didn't notice any particular smell. Thermostat has never been replaced. Waterpump was replaced about 4 years ago. I'm guessing the thermostat. Any other guesses? More importantly, is the thermostat on the left or right side (facing towards the back of the car), from the bottom (left) or top (right) hose?

[Mx5guy]

Sorry for the late response this problem should have been solved already but while thermostat could be bad the first thing to check is for proper cooling fan operation as thermostats tend to last more than coolant temperature sensors, some cars have a fan switch for this purpose (responsible with fan activation)