boiler refil problem.

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Hi, got a bit of a problem here, drained down the oil combi boiler to fit a new expansion vessel and refilled to 1 bar, set it to just hot water and let it run to heat th storage tank after five minutes the pressure started rising quite quickly and it switched off.The pressure continued to rise until the pressure release valve kicked in hissing slowly, with the pressure still rising I manualy operated the valve and a big whoosh of steam came out, I held the valve for a long time until the pressure went back to zero and still no water out the valve.So what's happening, air lock?Thanks for any help guys.
 
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There was a lot of trapped air which I have bled using the relief valve and refilled until water came out the relief valve, going to let it cool for a bit as the compression fitting on the relief valve was leaking so need to try to tighten it a bit when it cools.
 
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Yep, sounds like you had an airlock in the boiler, or simply didn't vent the system properly when filling. If it's settled down and the system pressure now holds steady around 1.5bar then all should be good, keep an eye on it as it may need bled and topped up after a day or two once all the air's out
 
Think it's probably all out now as the relief valve is at the highest point in the boiler so is good for bleeding, think the auto air vent might be goosed as when I take the cap off there is water up to the top of the valve right under the cap.
 
Can anyone tell me if the auto air vent is knackered by the photo (note the water at the top) and will this isolator that is leaking need the rest of the pipework releasing to replace and can the olives be reused or will I need to replace them, thanks.Edit wrong photo added and can't edit the photos on my phone, will post bellow.



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Last edited:
Well i fitted a new aav tonight and had no problems refilling as it just vented all the air out, old one must have been knackered.
 

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