I have a 2000 outback with 210,000 miles. I was driving the other day for about 15 minutes before i went to turn the heat on and noticed there was nothing but cold air coming out. I glanced at the temp gauge just as it pegged. I let it cool down and added some water before limping it home. After some fooling around with it i noticed that the top radiator hose was swelling as it would warm up. It would swell so much that when the fan turns on it rubs and makes an aweful sound. I checked the bottom radiator hose and it is cool to the touch when the top starts to swell, leading me to believe the thermostat needed swapped. I just swapped thermostats and i am now able to feel the bottom hose is getting warm as well. however, the top hose is still swelling. whenever I hit the throttle I can see the hose expand.
Have any of you had this issue or some similar? I'm afraid The head gasket will need replaced due to the rough idle upon start-up.