Nissan Repair: overheats 2000xterra 4x4, head gasket, wifes car

Question
my wifes car overheated I called the repair shop,that I truly trust He said check the fluids and bring it down.The anti-freeze took almost a gallon, I only added water,thats all I had. A 4 mile run, the car seemed to be ok I followed my wife and did notice a fare amount of white smoke coming from the tail pipe The shop checked out the car and said the car was fine just low on fluid, good to -27degrees the car over heated on the way home Called the shop and they said get it back and they would change the thermostat After letting the car warm up for about 15 min. the top hose seemed to be alittle warmer than the bottom hose I was going to give the thermostat a try my self  but wasn't sure if it was the top hose or the bottom and if it might be possibly the head gasket that I'm not going to attempt

Answer
Hi Martin -

At operating temperature (about 5 minutes of idling) both hoses should be warm or hot. If not, then replace the thermostat (bottom hose).

White smoke that dissipates quickly is actually steam coming out of the exhaust, which may mean blown head gasket. Have the compression checked, and that should tell you what is going on.

Hope this helps -
aloha
calvin