My 97' Eddie Bauer Explorer
 

Recently while driving my truck no more than 26 miles to and from to work
my temperature gage will fluctuate to hot. But as I check under my hood
the engine's cool. My on-board computer also says "engine temp ok." As I
stop for a minute and let the truck idle, when I take off again the temp
gage will move back down quickly to almost half. If I cut it off for 5
minutes and take off again the gage is all the way back on cool. What does
this mean?

Had the SAME problem ! It's your Thermostat ! And it WILL leave you on the
side of the Road ! I have a 1997 Ford Explorer XLT, a year and a half ago i
put it in the dealership and told them to have at it, they changed out ALL
the filters, belts, timing belt or chain, bearings, plugs and plug
wires,PCV Valve, thermostat even though the one on it only had 20,000 miles
on it, new shocks, new brake rotors and pads all the way around. I spent
almost $3,000. and also had something on the outside of the automatic
Transmission changed but it turned over 100,000 miles around last Christmas
and it's still running like new, you just HAVE to keep them maintenanced !!!
!!!I had an accident that left me crippled and rather than get rid of my
old Explorer i let my brother use it so i put it in the shop and had them
make it "LOT" worthy and then bought a NEW 2003 4x4 LIMITED Escape and they
refunded half the money for the work they did on my Explorer for buying a
NEW vehicle. the Escape turned out to be a LEMON !!! We're in the process
of getting our money back or a 2003 Explorer instead of the Escape ! I LOVE
Explorers !