Worcester highflow 3.5 BF- Auto Air Vent

[Zehroni]

Dear all,
There is always drop of pressure in the system, when I fill it to 1 bar, then a demand for DHW and CH is made, the pressure build up gradually as the system heats up and the pressure gauge registers over 3 bar. I also noticed that the Auto Air Vent leaking very hot water from its little black cap. One week later the pressure gauge reads 0 bar when the system is cold and around 2 bar when the system is hot.
My questions are:-
Is this normal?
Is the Auto Air Vent faulty and needs to be replaced?
Does this effect the demand for the DHW as the system shut down sometime closing the gas valve when there is a demand for DWH only?

Many thanks

 

[bengasman]

expansion vessel flat or dead, searh forum

 

[Zehroni]

Hi Bengasman,
I can not understand what you mean, please explain more.
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[bengasman]

i meant search forum, not searh forum.
common problem, see faq

 

[Zehroni]

bengasman,
Many thanks I am going through FAQ now, I understand I need to replaced the expansion vessel OR recharge it. Do they come pressurised from the factory?
I still can not understand what Auto Air Vent is leaking even when the pressure is below 2 bar. Would make any difference if I block the little hole at the top of plastic cap.

 

[bengasman]

Aav leak did not register with tired and limited brain. If it leaks, replace it. need to isolate and drain boiler first