So I was crusing around last night it was about 60 out. My car ran about 180 all night . Then after about an hour or so of driving the temp. started to drop slowly. I then had to go on the expressway and the temp droped all the way down to 130! I parked the car for about 10 min then when I got back the temp was at about 160. So I rulled out the gage not working ? Then I started driving again and it quickly droped down to 130 again. Anyone have any ideas. I have an aftermarket mech. gauge.