Howling like a dying animal.

[kaboom]

Worcester combi. Drained down twice in last fortnight for rad work. Dirty water in system I was told. Boiler now started howling when it gets hot. Occurs quickly when on hot water, takes longer when on CH. Pump gets too hot to hold but spinning. Howling varies if pump speed reduced. (Book says must be on full). Pump bled, aav working and power flush didn't cure it. My man reckons crud in heat exchanger. Wants to clean pump and h/e. What do you reckon chaps?

 

[croydoncorgi]

If pump is howling, it's probably been running dry (and likely also damaged beyond repair by now!)
Likely cause: air in boiler because AAV not working properly when system refilled.

What is indicated pressure on system?

 

[racket]

Are you sure there isn't a dog sat on top of your boiler

 

[jofly24]

If pump is howling, it's probably been running dry (and likely also damaged beyond repair by now!)
Likely cause: air in boiler because AAV not working properly when system refilled.

What is an AAV?

 

[ChrisR]

Automatic Air Vent.
I've never actually known one be damaged by running dry. Though I've heard some really loud ones which were running dry at the time, they've all shut up when water was restored. Worn out pumps can sound awful certainly, and if they run dry they get hot, but they don't seem to be damaged quickly by doing it.

I put a boiler in a loft and a week later a rad leaked the water out. The pump howled for an hour or more - the neighbour complained! That was 4 years ago and the thing's still ok. (Icos boiler with integral Wilo pump)

 

[PEDANTICVINDICTIVEMAN]

Stick some X200 and X100 in it, should be quiet after a couple of hours.