ok i have a 97 ranger, 4.0, 4 wheel drive 136,000. in the past week i noticed the temp gauge would (as soon as i turned the key and started the motor) jump to half way or over then as the truck warmed up level off at half way. so thinking it was the thermastat (and it being 7 yrs old) we changed it out. well we started it up and it did the exact same thing. so i can at least drive it and i shouldn't have to worry about it overheating but what could be my issue with the gauge reading wrong?