Not sure if Iam correct on this one so apdo correct me if Iam but there is a coolant called Waterless and higher the boiling point in fact I think it Doesn't boil or at very silly temp..!,An old Wheeler Dealers I think they put it in a TR6 and Ed took the radiator cap when the car was up to temp and running.
So if yours has this in the system you may not requie expansion bottle,plus another thing it is lifetime no need to change like a normal Antifreeze that you need to change.