Well firstly eliminate the air lock by removing the filler cap from the expansion tank and run the engine (also squeeze the coolant hoses making sure of any moving parts). If you have any air in the system, it should show as bubbles in the expansion tank. If your engine is overheating (going into the red) within the first 15 mins of the engine running then I would suspect the thermostat. The other thing to check would be the heater control valve, in relation to the overheating and also the lack of heat in the car.