I have a 1989 F150 5.8L. The engine light came on and I noticed the temperature gauge was pretty high. Soon it was all the way in the red. No steam or anything, just the gauge pegged. I stopped for a while to cool down and then started home again. As I was driving the gauge went way down to cool for 2 minutes and then back up. By thetimer I got home (2 miles) it was on red again. There is no other sign of overheating.

The top radiator hose was hot and the bottom was not too hot. I checked wires and all look ok. Could this be a bad sensor? Any suggestions?

 

check radiator cap seal, system may not be pressurizing(SP).

 

Check the fluid level after it cools down. If it's really low you found your overheating problem, but you still have a leak somewhere. If it's not low then you likely have a blown head gasket.

 

I changed the sensor for the temp gauge tonight. $4.99 at Autozone. That seems to have fixed the problem. If not I'll let you know.