I have a 1989 Ford Taurus GL with a 3.0L V6 Vulcan. I replaced the thermostat and coolant a few months ago and ever since I have done that the temperature gauge is acting weird. When its started in the morning and warms up, the gauge goes up to about 1/2 way and then starts to creep over the 1/2 way mark, then the gauge drops to 1/3 warmed up. It will keep doing this, fluctuating back and forth, and the severity of it going back and forth slows down and then goes to one spot after a while of driving. It also kinda overheats when I am in like a drive through and its all the way warmed up. the gauge will creep up over 1/2, but not quite 5/8 of the way. Then when I start driving it goes down. It didn't do this before I changed the thermostat. I need to know what the temp of the thermostat should be, I think this one might be 185, though I'm not sure. I will change it if I have to. None of my parents cars do this, and my dad even has a ranger from 1995, so somewhat close to my cars age. Please help.