Engine running hot

[HVACguy]

Hi all. So maiden journey in my 1989 Winnebago Warrior, Ford Econoline 350, 460 motor. Travelling from New Mexico to TN. Upon leaving Albuquerque, noticed temp gauge sitting on the L in NORMAL, thought " ok this is a little warm for my taste, but its still in NORMAL range" so continued down road. Pulled over at Wagon Mound NM to take a pic, left engine on and idleing for about 2 mins. When I got back in I noticed the temp needle had moved down to the M in NORMAL, which is where i would expect it to be. Drove the next 100 miles to Clayton NM, and the needle stayed in what I consider the ideal range on the M. stopped in Clayton to fill up, turned off motor. Upon starting back up, needle went back up to L and stayed there for the mile ride to Campground.


Got up in the morning, got everything ready to go, checked fluids, Coolant was about a quart low, ( no overflow tank present, just the tube from cap) so topped off, started up and pulled out..10 miles down road, needle at high end of L, noticed hood was loose, so pulled over, got out and shut it, get back in and notice needle just past L. I give the pedal one good rev and let off, needle shoots toward HOT, then back down to L, So now Im worried, I know that theres 300 miles of pretty much nothing between me and next scheduled campground, so I turn around and head back to Clayton RV park. upon pulling into park, i stop and idle and needle falls back into perfect range around M. Spend rest of day pulliny thermostat, checking hoses, and I have been advised it may ne fan clutch which I cant get until Tuesday as I am in middle of nowhere. Any thoughts, advice would be greatly appreciated. Thanks in advance.

[Rickf1985]

A clutch fan will engage when it gets hot but usually when you are traveling down the road there is more than enough air coming in from road speed and the clutch fan is disengaged. It would normally kick in at idle when there is no air being forced through the radiator. The fact that it jumped so quickly up and down makes me think it may be an electrical issue. The sensor would not react that quickly to water temp. You might want to check all of the small wires going to the body, take each one off and clean it and retighten it. There are several around each battery if you have two batteries. they are at both front corners and there are sometimes one or two underneath the battery tray. They would be the ones to really look at.
If you have one of those infrared laser thermometers you can point it at the thermostat housing when the pointer is on the "L" and see what the rearing is. That is the best way to see what is going on.  It is entirely possible you have a bad sender or gauge.