I am having a problem with my car still overheating... I have replaced the water pump, thermostat and radiator cap... it only overheats when I am hard on my car after about 5 minutes, but when its idiling it doesnt overheat. I am thinking that it could possibly be a heater core and radiator playing a part... could you help me please...

 

try to run water through your heater core! This will tell you if it's clogged. Let me know if your not sure how. Is your fan coming on?