I noticed today pulling my horse trailer home over some mountain grades that it ran a tad bit warmer than usual. Normally it runs a Needle width LEFT of center ( 200) or dead on center. When pulling grades towing is can get 1-2 needle width's to the RIGHT of the 200 mark. I noticed tonight it was a bout a needle with further to the right. Still way in the normal range. It was extrelemyl HUMID out. Would this have an effect? ALso noticed it took LONGER to cool down after I reached the top of the hill. When I stopped for fuel and let it idle, it stayed about the 200 mark for a good 10 minutes or so... Thanks!1

 

When was the last time you rinsed out the radiator and a/c compressor? I notice that when mine starts running a little bit warmer than usual, a quick rinse of those two items seems to help almost immediately. It's amazing how many bugs and just plain GUNK can get into the radiator and compressor.

Just remember to rinse or spray from the inside out - i.e. from the fan toward the front bumper.

I'll also notice the truck running a bit warmer the higher the humidity goes. And as far as the cooldown I notice my truck cooling down much faster if you run the idle up to around 1300-1400 rpms or so. Seems to move a bunch more air through the system.

 

I figured humidity had a lot to do with it!!! Thicker air to get through there. Thanks!

 

Yup sounds exactly like how mine reacts.