You guys have some great ideas however I think I'm going to wait until I tow again before I get too much more excited about this issue. It will be a couple weeks before I tow again since I'm living in my fiver while working out of town right now. Here's why
I drove from phoenix to flag yesterday (empty) but very aggressive with every effort to heat up the truck while having the autoenginuity software running on my laptop the whole trip. I could only get it hot on the major climbs running hard (Smarty #9). Some observations I noticed are as follows and all based on the AE software during my trip. I'm able to monitor several things digitally but chose to monitor coolant temp, fan speed, engine load and what I can only guess is the percentage of power sent to the fan for percentage of lock up when required (I don't know the abbreviation of the term used and will have to confirm)
The fan speed for the majority of the trip spun around 300-600 rpm's when just cruising down the road no matter the RPM when there's no significant load. The digital coolant temp seemed to match the gauge on the dash and when it would fluctuate even minor amounts and for the most part, it ran 195 which on the gauge is where the needle covers the 200 degree mark line. When I really tried working the truck hard could only get the engine load to come up to about 60% and noticed the fan speed would not increase until 205 degrees minimum at which point it looked as though the percentage of power to the clutch fan would vary from 15-89% causing the fan speed to increase to about 1300 rpms which is as high as I could get it to go and that is with the engine at 2800 rpms in 6th gear climbing a grade. At that speed, I quickly run out of hill to climb and the truck would cool down and things would be fine.
So I suppose everything is working as it should. I do not understand why the temp gauge in the dash never moved more than the width of the needle for 100k + miles and now all of a sudden its moving 3/8" to 1/2" when towing. Nothing is boiling over and there is no loss of power so far. To answer a couple questions, my radiator is very clean on the outside. When I flushed the coolant and changed the stat, there where no signs of corrosion or mineral buildup like I've seen in other vehicles. Next time I pull my fiver, I'll connect the laptop again and I will let you guys know what I discover.
You guys are great, consistently providing members invaluable information, ideas and resources that are truly a blessing to everyone!!