About six weeks ago, while sitting at a stop light, I noticed my 2002 WRX was steaming a little under the driver's side hood near the front. It wasn't overheating but there was a slow simmer of steam coming out. Then, about a week ago, the car started overheating up to -but not over- the red zone and would then cool back down to a semi-normal level. My first thought was a sticky thermostat so I changed it with no change. Here's what I noticed while looking around changing the thermostat:
1. There was a small amount coolant on top of the radiator and various places around the radiator but not a LOT.
2. The coolant level wasn't abnormal.
3. The coolant looked good, not bad or dirty.