Over Heating issue

[Twin2turbo]

A couple of weeks ago I had my radiator flushed and new antifreeze put in. Then a week later I had they thermostat got stuck open I replace the thermostat and the temperature sensor. NowI am pulling a travel trailer from Oregon down to Texas. The first day I did over 500 miles with no issues. Second day the truck started overheat. When the engine RPMs get above 2800 the temperature starts to go up. If I leave it above 3000rpm for too long The temp go all the way to 260. Ambient temperature is only about 50°. I’ve pulled heavier trailers in this before and never had this issue. There does not appear to be any air in the system. After replacing the thermostat I had to add 3/4 of a gallon of 50/50 mixed antifreeze. The orange stuff. I’m wondering if I should just use straight antifreeze or if I got a bad thermostat from Napa?

Does anyone have any advice or ideas?

Thank you.

[CamGTP]

Likely a faulty thermostat. Very possible that the new thermostat isn't working correctly.

[Twin2turbo]

Another new thermostat fix the problem, so far. I stopped at NAPA in Utah and bought the same thermostat again. The next morning somewhere in the middle of New Mexico I replaced it. Seven hundred ninety mile later this one is still working. 

 

[mikeyk101]

I had a similar experience with a NAPA part some time back. There was a mod to use a Carter fuel pump on my bike. It was NAPA branded. First one died within a couple weeks and I was able to return it and get a replacement. I gave the bike to my son in law last year and it is still going strong...

[Twin2turbo]

NAPA refunded me for bad thermostat. And luckily it was an easy part to replace.