my 99 2dr 4x4 just started showing very erratic readings on the temp gauge. Today on my way to lunch, the gauge got up to 240+ but there were no other signs of overheating. I got home from work, swapped out the T stat thinking that maybe it stuck. The problem still exists. The temp gauge will move from 190-195 (where it always used to stay) to 220, then sometimes come down to 180, then jump back up to 240. The movement of the needle is smooth, and it takes about 5 seconds to go from 190-240. It will do this whether it is idling, running down the freeway, or cruising at 40. Air temps today were in the 70s.
Any input would be greatly appreciated,
Chris