95 Deville 4.9 low coolant temp.
My 95 Deville with a 4.9 will not heat up past 170 degrees Fahrenheit while driving, but it does fully warm up past 200 if let to sit and idle. I replaced the thermostat with a new 160 rated thermostat & Still having the exact same issue. I read the 160 rated doesn't even fully open until 180 and if I am moving it won't go above 170. The heat does blow warm air but on extra cold days, it isn't hot enough. If it sits and idles long enough to hit 200+ the heat is as warm as it ever needs to be and once I start driving it will cool down from 200+ down to 170 in a matter of a few minutes So basically I know the coolant is a perfect 50/50 mix & it has a new thermostat. Any help would be greatly appreciated