I have just moved into a house (new to me)

I have a Worcester Combi boiler which works OK and is, so I'm told, only 3
tears old. I understand in a rudimentary way how these things work but not
enough to work on it.

I have the following problem which I think will not be doing the boiler any
good in the long run.

When I run the hot water and have switch it off the boiler makes a kettling
sound and when I'm up stairs I can hear air going into the bathroom radiator
which I think is the first radiator in the circuit, I have to bleed this
radiator every day.

I thought these things had a pump over run to cool the hot water heat
exchanger down after you have used it, also
kettleing happens even when the central heating is running but only when I
have stopped using the hot water.

Could anyone tell me if this behaviour is correct and how does the boiler
separate the hot water from central heating circuit. this kettling does not
happen when the cental heating is running only whn hot water is drawn off.

Also is there and adjustment to make to the pump over run work for longer
or come into action quicker on hot water setting to prevent this kettling.

MikeS