Worcester Bosch 28i Junior banging/kettling on heating only

[jsl123]

Hi, my boiler is about 7 years old and when the heating is on (DHW is fine no noises, etc) I get a kettling noise which occasionally becomes louder like pop corn with the occasional louder banging. This started about 2 years ago and has steadily got worse although during that period it can stop completely for months/weeks at a time. In addition it used to be that quite often once the noise starts, turning the thermostat down on the boiler and back up to temporarily switch off the ignition cures it for that period of heating.

The output pipe quickly becomes so hot it is impossible to touch whereas the input remains relatively cool for a while. I live in harrogate so don't think it is a scale problem, and guessing pump related. Any ideas?

For history about 6 months ago I had to repressurise the expansion tank which I worked out was low due to the idle water pressure repeatedly dropping slowly and realised it was over expanding and venting because of this. Inititally thought it was either a leaky radiator or valve on the filler loop which i'd mistakenly left connected.

Any suggestions before calling an engineer round

 

[Al-Glasgow]

Has it been serviced over the 7 years ?

 

[jsl123]

Has it been serviced over the 7 years ?

Sorry forgot to add that, yes it has been serviced about once every 18mths on average. Was serviced/checked 12months ago but of course behaved itself when the engineer was here and my descriptions of the problem didn't seem to bring any look of worry at the time.

 

[bellairaphon]

pump. u can swap the head but sometimes u get a small leak changing the pump block requires loosening a nut inside the combustion chamber. a good repair engineer should have it swapped in half hour. but u could just swap the head see how u get on.

Nath

 

[bengasman]

...it has been serviced about once every 18mths on average. ....

How long does it take to do the service? Do they actually strip the boiler?

 

[jsl123]

How long does it take to do the service? Do they actually strip the boiler?

Less than an hour from memory. They remove the case, access the burners, etc but not stripping it down to the heat exchangers, say.