Engine temp question?

I noticed tonight while I was idling in a parking lot for about 10 minutes the temp guage went really high. After I left it dropped really quick to normal. The temp outside was about 40 F. After driving around I thought I would see if this would happen again and it did. Last summer I changed the radiator, thermostat and hoses. Never noticed this before. Any ideas? It's a 96 Ford F150
Engine temp question?
a good test for the fan CLUTCH is



let engine idle after warming up, hood up

shut off engine

watch fan- if it keeps spinning, clutch is shot



if it stops abruptly, clutch is good



bad fan clutch will cause overheat
Engine temp question?
Make sure you have enough coolant in your system.
Sounds like thermostat is sticking. It blocks off water flow to the radiator till it reaches a set temperature specified by auto manufacturer.
Change your thermostat. Its going way to high before finally opening. Too many times and you will have to replace intake manifold gsasket or worse. Good luck!!
Could be a thermostat, could be a faulty fan clutch, could also be a bad radiator cap as unlikely as that may sound. Make sure your fan is spinning and it should spin faster as the truck gets warmer.
Hello what I would check for, make shure the coolant level is ok,the Radiator is not stopped up, hoses are not collapsing, the thermostat is opening up,and check the fan clutch. If the fan clutch is free Wheeling then the fan will be rotating very slowly, causing the air not to flow through the Radiator to cool the coolant in it while stopped and when you start driving air will be forced through the radiator and the coolant will cool off. Also stick a manual thermometer in the radiator to make shure the engine is getting hot. It could be the sending unite or temp Gage. hope this helps good luck
i would definately check and see if your coolant fan is working. thats what it sounds like to me.