Banging and popping Worcester 24i

[barne_As]

I have a worcester 24i junior boiler and have recently noticed that when the heating is turned on, the boiler lights and then about 15 seconds later the boiler seems to pop and bang for about 1 minute, After this the heating runs normally and no further banging.

The pump is rotating, i have checked by taking the cap off. I have checked the expansion tank and its at the right pressure.

It seems like there's air trapper in the system but i cannot get it out.

I drained the whole system and the expansion tank. I then re filled it all and the automatic air vent was open as i heard air escaping but i cannot find the automatic air vent!

What else can i do or does anyine know the answer!?

 

[ChrisR]

AAV is at rear of pump. Make sure its cap is loose.

 

[pannierstan]

AAV is at rear of pump. Make sure its cap is loose.

I thought it was ontop of the heat exchanger inside the combustion chamber. Are you thinking of the Greenstar Junior Chris?

 

[barne_As]

Ok, ive foudnd the AAV. Its behind the pump and the pump needs to be removed to get to it. It is open, as ive heard air coming out of it when i re filled the system.

Im still getting really loud banging noises when the heating is turned on. It seems like its coming from the heating exchanger (the bit on top of the burner) as this feels like its vibrating when the banging occurs. Heating and hot water still work fine, but i have noticed that when i turn the hot water on with the heating, water shoots out the hot tap, then stops then settles to a constant flow. What is this and hiw can i fix my problem??