Boiler banging noises

[keithpb69]

Hi my boiler is making a loud banging noise, when i first switch it on it fires up fine then after about 10 seconds makes a loud banging noise then shuts down, then follows a gurgling sound, it has got worse over time i'm thinking it might be the pump but don't know that much about boilers.. it would be much appreciated if anyone is able suggest anything else it could be..

the make of boiler is sime if that will help.

thanks..

 

[dontknowitall]

Pardon the pun, but it sounds as if there's not much water in the pipes. The pressure should be around 1.25 to 1.5 bar.

 

[keithpb69]

hi thanks for the reply, the pressure valve is on 0 until it is switched on then it goes up, it usualy reaches about 1 then cuts out.. should the pressure meter be on 1.25-1.5 constantly, i.e when the boiler is off?

thanks again.

 

[dontknowitall]

That's what I'd expect.

 

[keithpb69]

right, i sorted the pressure out by turning the screw on the filling loop, this has stopped the banging, thanks for that. i also have more problems, lots actually but i'll just share the one's with the boiler for now . The central heating part is working fine but only 1 rad in the house is heating up? and i am only able to get hot water when the heating is switched on? although not for long as it runs out quickly. when i turn the hot water tap on without the heating on the boiler does not kick in? any ideas please..

thank you.

 

[newbie1]

you really need to call an engineer/plumber as it cant possible be diagnosed over the net...there are too many variables ie was system flushed ever/do other rads get warm/what temp is hot water /what does guage reading when nothing on/it has poss divertor valve prob it could also be sludged up which may have in turn mullered the valve the pump could also have become shagged
to be honest by leaving it till now and not getting it looked at as soon as banging started you may well have given yourself a bigger bill than if you had got someone as soon as it started playing up
boilers are not something that can be fiddled with either

 

[Bernie2]

If you have had no water in the system. You will have to go around and bleed each radiator until you get all the air out, you get water out of the radiator air bleed when its full.

Its a bit of a pain to do and you will have to go backwards and forwards to the boiler and refill it, just relax and take it easy, it can be a slow job.

When you have done the air bit, run the heating and make sure each rads getting hot. Start nearest rad to boiler and work away for both circulation check and air bleed. If you have trouble getting it to the furthest away rad, turn all the others off usually does it. Might need a bit of a balance but I would try air and circulation first.

The thinking is: The system is part full of air and to get it out you have to bleed each rad.

Could be as Newbie said as well.

Has anybody taken the radiators off the wall recently to decorate behind them and not filled the system after putting them back?

Very common problem on sealed systems I should think. Especially if people have lived in a house with an open vent self filling system. They probably figure central heating is central heating. Its an easy mistake to make I think.

 

[keithpb69]

thanks for the reply newbie1, i am thinking the hot water problem is diaphragm/diverter valve, don't worry i won't tackle anything i don't think is safe.. how much would it cost to get this sorted if it is the problem? also thanks to bernie r.e rads i thought that might be the problem, thanks again for taking the time to reply both of you

we only moved into the house about month ago, so not sure how long it was going on for either

 

[newbie1]

going from the top the boiler should have a min of 1 bar pressure even when idle but you need to check manufacturer recom
if air is in there boiler will keep shutting down as air will overheat it and shut it down or it would go into orbit
if the system has never been cleaned out then sludge could be affecting the diverter and making the pump work twice as hard
the fact you get hot water but only when heating is on is a bad sign as it seem likely the divertor is at least partially stuck
what colour is hot water
its poss the sneaky swines had a problem and drained system before leaving as water in a sealed system only has 2 options one is to circulate and the other is be drained or leak there is nowhere it can go unless the system overpressurises and the prv blows it out
check outside if 15mm copper pipe that should come out and face back to the wall shows signs of water blow out
tbh a power flush wld cost around 200.00 to clean system out and may well cure the other problems but without a visual on the boiler its not easy to say

 

[keithpb69]

cheers mate, since putting pressure back into the system it is running fine and quiet for the heating, the hot water i do get while the heating is on seems o.k colour wise, it is a bit cloudy while running hot.. but it only runs hot for a short time depending on how fast i run the tap, but boiler won't kick in when just running hot tap.. how come i get hot water when heating is on? is this just sort of taking the water ment for the rads? thanks for your advise..

p.s it does seem like there has been water from the pipe you mentioned ..

 

[newbie1]

keep an eye on the pressure as if you are bleeding off from the heating side the water you are loosing out hot tap maybe coming from heating hence the lack of water
with regard to the hot water there should be a flow switch which when you turn on the hot tap it tells the boiler to call for action
but impossible to diagnose over the net ime afraid

 

[Bernie2]

Which Sime boiler is it?

Combis can work in a few different way.

No the hot doesn't take water meant for the rads in the same way you seem to mean. I am sorry if I misunderstand you.

A usual combi, redirects the water from the central heating heat exchanger circuit through to the hot water heat exchanger. The hot water you draw off comes right from the water main like an electric showers water. Only its gas not electric.

What should happen providing everything is alright, is that when you turn the hot tap on, the boiler should stop heating the central heating and heat the hot water. But some combis work on a stored water basis to increase flow.

So that is why I was asking what sort of SIME combi is it?

Perhaps you have a few faults on it other than what is obvious. It may be the hot water flow switch is faulty and not diverting the water from the heating to the hot water heat exchanger. It could be an open circuit hot stat telling the pcb its satisfied so don't divert the water. Simply loads of things.

But if we know which boiler it is we may be able to get a bit closer to the problems.

Hope this helps.