Truck Repair: overheat issue?, upper radiator hose, caterpillar c7

Question
QUESTION: Kenworth T300 with a caterpillar c7 , 250hp with 310000 miles, year 2004.

Hi, above is my truck's info. When I drive for 15 minutes, my truck's temperate goes up to 210 degrees and engine fan comes on, but still on 210 degrees. I think it is overheated. Can you let me know what needs to be replaced?
Thank you,
Garry

ANSWER: After the fan comes on if it starts to drop then everything is working normal. If it stays the same or keeps rising then your thermostat is stuck closed.

---------- FOLLOW-UP ----------

QUESTION: Thanks, so how do I fix the thermostat? Does it only need replacement? What is the normal temp?
Thanks

Answer
Yeah just needs replaced if you follow your upper radiator hose towards the engine it will go into a metal housing normally held on by 5 or 6 bolts. take that off you will see the thermostat in the housing replace that and theres a metal seal down in the housing when you pull out the thermostat replace that and bolt it all back up. Temperatures are anywhere from 180 - 210