Hello XXXXXX and welcome to Just answer.com, Super mechanic here. It sounds llike the thermostat is sticking closed. If the car is overheating and you are not getting any heat and the cooling system is full.
See if it will try to spit coolant back out when it runs with the cap off after it warms up.When the thermostat sticks closed it will actually shoot out when the engine starts to get hot and the coolant should circulate.
Or, you could take the thermostat out and heat it in a pot of water to see if it wil open at the specified temperature.
Master technician
29 yrs. exp., ASE master, cert. in G.M. electrical, a/c, susspension, brakes, electronic steering