Well, ive had the radiator, 2 thermostats and the computer replaced (I forget the technical name for it) on my 99 Ranger -Small v6 120,000 miles. I was recently starting out on a trip to AZ. from San Diego (mild weather) when my temp gauge starting registering HOT and then the needle fluctuated rapidly between Hot and Cold- now, when I got out and popped the hood the radiator and engine were still cool,so when I got back in and started driving, theengine started running rough and losing power, and it also started making that familiar rattling, linkage typenoise when i accelerated - much like it did when it really overheated in the past.
I suspect a possible water pump problem, but im not sure- - Any suggestions?

(P.S. when the Gauge started registering HOT, I tried turning on my heater full blast to keep the engine from boiling over, and I noticed all I was getting was luke warm air from the vents!?!?)
Thank You, Kevin.