This is what I have done. Flushed the Rad and system with a prestone 10 minute rad flush. The heater core and Rad was not blocked but it did clean my system out. I've tried a Stant and Motorad thermostat 195 and 192 degrees. Yes I replaced the Rad cap too.

This truck has always ran cool, even in 30 degree summer weather here in Canada the temp gauge might reach 1/4. I did notice after the rad flush in the pail I used their was some oil present at the bottom. My oil is clean and the coolant has never had to be topped up. No leaks, nothing. When I drive on the highway my temp gauge goes up slightly (not even 1/4) and blows good heat. Driving in the city it cools down with luke warm heat. To me its backwards to what it should be. The engine runs great and smooth with 180,000 miles on it. The Blend door works had to fix a vacuum leak under the hood which fixed the air flow direction only. Evey one I've talked to says its a blend door issue. If my water pump was weak would it not overheat? Would taking the clutch fan off be a good idea? It is not seized. Any ideas? Thanks.

I forgot to the add this, both heater core hoses are hot, top rad hose hot, lower rad hose warm only. Again if the W/pump was weak would it not overheat?