Getting hot!

I'm pulling a Terry Classic V22 with a Nissan Titan 4x4. Previously I pulled an R-Vision, Bantam Hybrid. The Terry is lighter, but stands higher than the Bantam. I never had an issue pulling the Bantam with the engine getting hot. It doesn't over heat, but will get hot, then it looks like the thermostat opens and the needle comes back to "normal". I'm using the tow mode, speeds under 65mph. I'm having the radiator flushed and fluids replaced. Starting with the easiest first.....
Your thoughts?

What temp is "hot" and what is the thermostat temp setting. I would check that before moving on. It could be a sticky thermostat.

may want to also add separate transmission cooler- if it does not have one- if not part of towing package the trans fluid will run through radiator as well and can actually add heat -

Replace the thermostat.

I don'k know about Nissan, but many vehicles have thermostatically controlled engine cooling fans. They kick in when the temperature hits a point somewhat above normal to cool things down. On my former chevy truck there was a noticeable increase in noise when that happened, then the temperature would move down to normal. Just an idea.

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Have your water pump checked...

Our Ford Escape was doing the exact same thing and just had to replace water pump last Friday!

The day before we had driven it in to San Diego and Mexico...glad it didn't die while we were down there!

While waiting in line to get back in the US of A is when I noticed it getting pretty hot...then cooling down over and over again.

And one other thought...

It is highly possible that you might need to get a bigger truck for that trailer.

If you've had the truck awhile make sure your radiator is clean and not being blocked by junk build up over time.

I seem to remember about a recall for a cooling fan issue but dont know what the specifics were othe than it was on older ones.