Yay my first post on moparforums.com!

Having a problem with my cooling system, hoping someone can offer a suggestion.

In July I did a radiator flush and thermostat change(160 degree ). After the flush and t-stat change, I noticed my temperature gauge would not read quite as high as it did before the cooling work I performed. I figured the cooing system was just working better because i cleaned all that crap out of the cooling system. The car ran with no problems running in temperatures from 80F to 110F.
Now, in December its much colder out with temperatures anywhere between 15 and 40 and sometimes colder. My car's temp gauge sometimes will not even rise past the "cold" reading and the heater is only about 75 degrees. There are times it wont even rise at all. Past winters i have never had this problem, the car always kept the correct temperature.
On the highway, the car runs at normal temperatures. The heater is hot an efficient.

Ive checked coolant, its at the correct level. Also, the water pump is new and heater core was flushed
also. Could my NAPA t stat be out already?

The car is a 1970 Plymouth Valiant, 65k orig miles. 3.7 Slant Six. Completely stock except for the addition of an evap cooler.

 

Could you have put it in backwards ? put a 180 deg thermostat in it. Did you flush the heater core ??

 

HI there
I flushed the heater core also and the t-stat is in correctly. I guess ill give a 180 a try, they are easy to install anyway.

 

I agree... It needs a 180* thermostat... That should fit it...