On the expansion tank if replace do thermostat also

What is your question?

But I noticed that the water boiling in the expansion tank is that normal are I'm looking at a bigger problem because I had a car with the same pressurize system and I had a blown head gasket I'm hopping that not the case it runs fine at idle no leak but when driven antifreeze is everywhere thank a lot hope you can help oh I'm sorry I don't have any gauges telling me that the car is hot only the smell and notice of antifreeze thanks again