Overheating while pulling boat.

Any ideas? 2004 F150 6 cyl 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 or changed the antifreeze. 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?

Start buy replacing the thermostat it is cheap and very easy to do. Or try going to a auto forum. I would bet somebody can pin point your problem very easily.
. Or google your truck problem with the make and model of your truck and something will pop up.
Good luck.

I would start by taking a very close look at our radiator fan clutch. If it is bad ,at higher speeds the force of the air coming through the radiator could slow the fan down and causing an over heating issue, a thermostat issue would result in an overheating issue at most all speed and not just while towing.

Sometimes when over heating the computer will attempt to shut down the vehicle to avoid severe damage.

JMHO, Jeff

The radiator may be getting plugged up and isn’t allowing enough water to flow to cool it properly under the extra load while towing. I would try a new thermostat first if there is no change my guess it is time to replace the radiator.

Cooling system flush and new thermostat are needed

X2, after that have them Pressure Test All of the Cylinders just to be sure you don’t have other issues like a leaky gasket or blown gasket.

Cheaper having that done than spending good money on a Bigger Problem.

Good Luck.

Ever changed the fan belt?

This happened to me one summer and the radiator was plugged up with dragonflys. Pulled into carwash and sprayed the radiator with the high pressure hose and never a problem since. Sounds like you have more going on but it would not hurt to visually take a look at the front and see if you don’t have a lot of bugs caught up in there.

Cotton wood will also plug the radiator fins and cause close to the same issue, blow them out wit high pressure air from the front of the radiator tho.

Many possibilities. Check for debris between ac condenser & radiator. Bugs,grass,leaves,etc. Fan clutch could be bad which would account for your loud fan noise.
If those things are OK I would replace radiator & coolant.

Could very possibly be the clutch fan – had mine go out on my Durango – same symptoms.