Actually you do not required to do anything now, I kept checking every week, my reservoir still above max limit. You can flush your radiator every year or 20,000km. The expert will do up for you no worry on your part. 
Hi Jazz,
thanks for your prompt replies.
ic. iagree, i don't have to do anything on the coolant and radiator except do regular checking only (but not everyday). only check when feel 'song' then check.
btw, your reservoir above max level is before you warm the engine or after?
now, mine coolant level is at max when it's in cold (every morning b4 start engine).
after driving and reached distination, i chk again, it is surely above max level.
thanks again. u r the man.
regards.