156,000 miles, I've been pulling a 21ft bass boat in the summer for years with no issues. Now on hot days (over 78 degrees) it is over heating. Can't use AC and need to slow down to 60 mph in-order to cool her down. Never have flushed the radiator but I'm wondering if getting it flushed is a waste of time and if I should just proceed to replacing the radiator? For a couple of years now I can hear a roaring sound (like a jet engine) on really hot days, when I start out driving. Could this be a cooling fan? Seems like the power is restricted during these times. Really need to increase throttle to get going?

 

I would say flush before replacing. I replaced my radiator a few years ago due to a rock and it cost over $400 . I think a flush is a more economical solution

 

Do you mean you have never serviced the coolant/cooling system since new? Or did you mean you have replaced the coolant a few times but did not do a back-flush? If you have never serviced the coolant, you could have a clogged radiator and a bad water pump. What does the coolant look like in the surge tank? Is it dark?
Also, its time for hoses. It is not uncommon to have a hose that has delaminated on the inside with a flap of rubber blocking the flow. It could also be the thermostat, but I don't know if Ford uses the 'fail-cold' thermostats. If its a 'fail-hot' one, that would be the first place I'd look. The 'roar' is most likely the radiator fan clutch, which is normal.
In any event, what you have is an insufficiency in cooling capacity. It could be something blocking the flow, a thermostat, the clutch fan, the water pump or internal corrosion from neglected coolant. When the old coolant fails, it loses its corrosion protection, and can attack the aluminum water pump impeller, sometimes so bad that it can hardly move the coolant through the system.

 

Saxman, I have never done anything. Never changed the antifreeze, flushed it or done anything else. Likely this is a violation of the pickup truck owners code LOL. But it seems that I have taken the "if it isn't broken, don't fix it route. The fluid is brownish. How difficult is it to change the thermostat on this truck? I see on Ebay that I can get a new radiator for about $100.

 

There's no 'pickup owners' code' that I know of, but cooling system maintenance is covered in the owner's manual. Brown fluid is bad and the cooling system will have to be flushed. Then the whole system can be checked to see what's causing the lack of cooling capacity. Good luck.

 

If you haven't changed the coolant and this truck is over heating I would have a hydrocarbon test done on the cooling system. You could have the start of a head gasket going. As cooling gets old it turns acidic and electrologist starts to eat away at the gaskets and metal. Before spending a bunch of money have the HC test done. Should be under 30.00 bucks for the test. Like was mentioned you my just get away with a flush and rad and t/stat.

 

This reminds me I should change the coolant in mine. It still looks good but after all, its almost eight years since the truck was assembled at the Norfolk plant. I now have almost 16,000 miles on it.