changed thurmostat heat worked now not working heater core hoses 1 hot other not on 2007 Pontiac Grand Prix

what should i do i need heat car does not over heat

Asked by for the 2007 Pontiac Grand Prix
heater core is clogged and needs to be flushed out. you need to run water through the core in both directions to get the dirt out. changing the thermostat and flushing the rad is a good idea as well.