Screaming noise from boiler

[gavin1974]

Hi,

Our combi boiler has started making a screaming noise when the hot water is run. It screams and drones until it switches off.

The boiler is a 1988 Worcester Highflow 3.5 combi boiler. We have only just moved into the house so not sure about service history etc. (there is a recent certificate for gas safety).

Any idea waht the problem may be?

Many thanks in advance.

 

[ollski]

Does it do it on the heating as well or haven't you tried it yet?, it does sound like the pump.

 

[doitall]

Perhaps the cats got stuck in the flue

 

[gavin1974]

I think it's only when the hot water is used.

 

[ChrisR]

This seems 2b the same?
//www.diynot.com/forums/viewtopic.php?t=27572

 

[gavin1974]

How do I flush the system? What is an inhibitor? How will doing these things help the problem?

(sorry for all the questions!)

 

[ChrisR]

You could try "boiler silencer" which you can inject at a vent point.
If no better then System Restorer, which you'll have to wash out completely before refilling.
If that doesn't work you're looking at Powerflushing with DS40.

If that doesn't sound easy/attractive you need a boiler bloke.

 

[ollski]

This seems 2b the same?
//www.diynot.com/forums/viewtopic.php?t=27572

highflow 3.5 has a storage cylinder and runs off a 3 port valve though, highflow 400 in other post is a combi with dhw heat exchanger, although for sure there could still be a blockage.