I'm afraid my head gasket is going to go. I can smell the sweet aroma of anti-freeze cooking on the hot motor. It appears that anti-freeze is lightly spraying out from the overflow res. I've topped off the radiator once since I've owned it. I bought it 5 years ago with 135K on it, I'm at 190k now. The previous owner said the head gaskets had been done. What are the earliest of early signs that gasket is about to fail?