rumbling potterton boiler please help!

[gingerb]

I have a six year old Potterton boiler. When we turn the hot water off the boiler makes a very loud rumbling noise, then goes into lock out - hot water also comes out of the overflow pipe. This seems to be worse when the heating is also on.
A British Gas boiler specialist has told me we need a Power Flush because we have a build up of sludge. However I've been told this is often a stock response and am wary it may not be the case - I don't want to fork out unnecessarily (I'm aware other companies will do it for less money).
I'm told another symptom of sludge build up is if the radiators are cold in the middle / bottom and this is not the case.
Does anyone have any other ideas as to what it could be, or does it sound as though the diagnosis could be correct? Any help gratefully received.
Thanks!

 

[Rob]

Sticking flow switch on a puma

What MODEL boiler is it?

 

[Agile]

I
A British Gas boiler specialist has told me we need a Power Flush because we have a build up of sludge. However I've been told this is often a stock response and am wary it may not be the case -

Does anyone have any other ideas as to what it could be, or does it sound as though the diagnosis could be correct? Any help gratefully received.
Thanks!

I dont think he is much of a specialist if he cannot diagnose a stuck switch on a Puma! ( They are also sometimes called a Combi 80e )

But you should have told us that your boiler is a Puma rather than leaving us to guess!

Tony

 

[gingerb]

Aplogies, it's a Potterton 100 or 1000 (I think 100). Do you think the power flush is unlikely to be needed?

 

[Agile]

Sounds like a Combi 100e which we call a Puma.

I dont know why you still think a power flush is necessary when totally impartial experts have given you the answers!

BG engineers get a commission when they "recommend" you have a powe flush and you accept. Some people will do anything to get £10 whether you need it or not !

Tony