this happened to me recently - than i realized that its possible the collant froze and when the engine gets hot it unfreezes
i left it alone since the warning went away
no more warnings unless its cold (overnight) engine so it must be the coolant freezing IMO
"EVERY FORM OF REFUGE HAS IT'S PRICE"
2002 4.4i BMW X5 - 166K Topaz Blue Ext/ Tan/Beige Leather Int
1994 Nissan Pathfinder SE 132K Black Ext / Grey Leather Int