Hello, I have a 2002 v6 mustang base model. Over the winter it over heated and dropped a plug on cylinder #2. I replace the thermostat and it went away. Now that the weather is gonna and it’s getting warmer it’s overheating again like it’s pushing the radiator fluid into the over flow but not back to the radiator. When I checked everything out I noticed I had oil in my coolant but no coolant in my oil. Could this be a head gasket causing the whole issue.? When the car overheats I pull over release the pressure out of the radiator and the it sucks the coolant from the reservoir back into the radiator. And help will be appreciated.