when i start my boiler up from cold i can hear the water making a fizzing sound as it goes through the pump i presume.ive had the system flushed using x400 to make sure there no sludge or corrosion in it and refilled it with x100 and x 200 in

this has gone on for a few year now despite bleeding the system numerous times no air comes out and also the pressure has always stayed at 1.5 so idont think its pulling air in

you can here the fizzing going around the radiators in the house until they get warm then its quiet.

ive had the bathroom radiator off which is the first to get warm and started the boiler up and opened the lockshield valve and for a few seconds the water splutters out in bursts the runs ok im guessing there maybe corrosion or something inside the pump causing this apart from this the house heats up no problem

can anyone help as its doing my head in now ive tried everything i can/allowed to do

Sounds like air in the pump. Has the pump been bleed from the screw in the front?

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the air release screw on top of the pump? thats open if that is what youre talking about if this is the problem what else can i do to sort it like i say once the heatings been running for a bit everything is ok ( iguess the air release valve is doing its job) could it be i need a new pump

Possibly a new pump, but it sound like air, from what you wrote. On the front of the pump is a screw which you can release any air (should the AAV the screw on the top) not be doing it's job. If that doesn't do it then it does seem you have a circulation problem. You will need to have the pump checked to see if that is the problem, but it could be a restriction either within the boiler heat exchanger or the flow and return pipes. Without testing it is difficult to advise.

Suggest you get an RGI in to check and advise.

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do i open this screw while the boiler is off? id imagine i would as the air will be there but wanted to double check before i do it

Don't touch the small screw on the body of the pump.

You want the big one (chrome) in the center of the pump.

Boiler turned off, and have a bowl to catch any water.

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yeah id guessed it was the big one when i saw the arrow on it.well i did it once the screw started to loosen the water that was there sort of spluttered out untilthe screw was fully loose.tightened itup and started the boiler i couldnt hear the fizzing noise i could before when starting it up however i went down stairs and my kitchen and living room radiators were making thatsound which went on for couple of minutes till heating warmed up then its totally silent.tried to bleed those radiaotrs while you could hear the fizzing soun making its way around the radiator but was just getting a steady trickle of water out no air

Always have the boiler and pump off when bleeding anything.

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its got no better since i removed the chrome screw on pump if anything its worse.when heating starts up every few minutes u can hear what sounds like bubble/fizzing through a couple of the downstairs rads(it does stop doingthis after a few minute after the water has been aroound the system a few times) after.onething i noticed today was i had the heating for couple of hours i filled the sink up with hot water.as soon as i stopped the water i could again hear the fizzing/bubbling noise going through the radiators until the were ht again.

im no expert on heating but would thissuggest a problem with the heat exchanger as mention in previous post

You need to find where the air is coming from it can't suck in with a sealed system.

Are you getting air form any of the radiator.

Does any air smell strong.

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get no air out of any radiators steady stream of water.when i hear the fizzing noise going around the systems ive tried shuttind down the radiator its gone into and bleed it off later that day but no air comes out

Do any of the radiators have TRV's on them?

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all of the them apart from the bathroom one which is the closest to boiler and gets the concern first.one thing ive noticed when i turn the heating off around the pump area you can hear a fizzing sound

cant really smell it because of the inhibitor,but when i start boiler i go into bathroom wait for the bubbling to enter that radiator(closest to boiler) once its passed the valve i turn the other side off.if i leave the radiator for a day or so i then can bleed a fair bit of air out but once i reopen the valves the next time i use system its back

I would suggest that it is not air in your system but hydrogen which is caused by a chemical reaction from hot water and iron. Usually treated with a good flush and an inhibitor to inhibit the corrosion process. Even though you have had it flushed, hydrogen is still being produced, which indicates perhaps not enough inhibitor has been added for the size of system. The water can be tested to confirm.

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