OK, so all of a sudden I look down and the thermo gauge jumps up to max right in front of my eyes. This is becoming more and more common. If I pull over and shut the truck off it goes back to normal. What do you guys think sensor? Thermostat? Need to fix asap please advise! 2005 5.4 SCREW....

 

I'd make sure it's not overheating firt off. Check your coolant level too

 

Probly the thermostat

 

sounds more like the cylinder head temp sensor. if it was really overheating, it would take awhile for the temp to drop back to normal. need to get ahold of a good scanner and an infared temp gun. monitor cht and and when the gauge shows hot, check the cht reading and then use the infared gun and check the actual temp of the engine and compare readings. or just throw a cht sensor at it and see what happens.

 

OK. Ill get a new sensor... Are there one or two?

 

If it is not really overheating, watch the other gauges too. Gauge fluctuation is can be a sign the battery is going out.

 

Other gauges are fine.... I ordered two sensors. Ill update as I go.

 

Ok so I got the sensors..... Looks like these are UNDER the intake?! Aaargh... Anyone know of some directions for this?

 

Anyone?

 

OK guys. For the record it was the thermostat.

 

That's what I figured, same thing mine did, its like all the sudden the thermostat would open and pow, temp would drop