it does dound like you have an air pocket in your cooling system --
easiest way to get the air bubble out is.... make sure coolant resevior is to max fill line
with car at operating tempature... turn the heater on full heat and fan speed 1.... then put car in first gear { back road } and get your engine RPM up to around 3500 to 4000 RPM-- keep the RPM up for at least 45 seconds in gear.
the air bubble will be forced out the radiator into the coolant resevoir..
hope this works for you... has worked for me many times
