Backflush the heater and radiator, also maybe replace the pressure cap. I would change the pump, if it is plastic impeller, impeller could spin on the shaft when hot. The head gasket could be bad, but the heater should still work as far as I know. Cooling fans are trouble, easy test see if it comes on with a/c on. Then see if it comes on with warmup "m" or so on the normal scale.
