Today while driving my 1995, 6.5, I noticed that the temp gauge would jump to around 210, then above, then below, all very quickly. Then it held at around 210 or slightly higher for a while then dropped to slightly below, all while maintaining the same speed (unloaded on level grade). Truck has alway been rock solid on temp gauge, unless towing. The temp usually always holds at around 2-3 clicks below 210 and never budges. No problems with radiator and all is clean. Any chance the problem is the thermostat or sending unit, or possibly a bad water pump?????? Anyone else had these problems???