Well the coolant should only reach 206 Degrees F when thermosat is fully open. You may have air in the heater core or a larger bunch of air that needs to be bleed. To fdo this;
Let the car cool off and reove the radiator cap. Get some 50/50 radiaotr and distilled water mix.
Trun the heat control to the highest tmeprature setting.
Allow to reach operatin temperature and top off readiator and reserviour.
See if that helps.
Monday, July 10th, 2017 AT 6:30 PM