What do you mean by an air lock?
In the boiler or in the system? C/heating or hot water?
What is the actual fault as I have no clue as to what you mean by an air lock with this particular model - Especially as I've never even heard of a 50E... They make a 105E and an 80E; or there is a Bermuda 50/E - But not a Combi 50E...
Reconsider and post again with a little bit more info.
GasAid.co.uk
January 2007
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