My brother had the same problem and it was his main fan not turning on. Run it... Check it....and get back...

I just put 180 degree thermostat in, and my fans dont turn on till 200 degrees it usually doesnt go over 180 unless im waiting in line at wendys or taco bell your radiater is probably bad, check your water pump make your cooling system isnt clogged up or anything like that. yester it was 90 with 87 percent humidity still stayed on 180 degrees mines a 92 se with 195,000 miles on. but that is the problem about haveing cast iron engines.