Vaillant Ecotec 831 water pump noise

[Wictod]

Hi,

Hopefully someone can diagnose the problem I have here. Have an Ecotec 831 that works ok except for the fact that when the boiler has finished heating up (it's reached temperature and start starts to idle beofre the pump stops) there's a knocking sound which is coming from within the water pump.

The odd thing is that when the boiler is burning gas and heating up you can't hear an issue or feel any vibration, only when the gas cuts off and the pump is still circulating water is the knocking evident? I don't think it's coming from the heat exchanger either as I can hear a knock from the pump along the end of a screwdriver.

any ideas? pump bearing knackered?

Regards

 

[Phill Peck]

How old is it?

Some models of the ecotec had a wilo pump which was shocking, although mine is @7years+ with a wilo still working fine nice and quiet

 

[Wictod]

it's 7 years old and has got a Wilo pump for sure. It's ok when its burning gas for some reason but knocks when its just pumping and hot.

 

[mickyg]

pumps gone into self destruct timer mode. I give it 3 months.

 

[Wictod]

bummer, oh well, at least its kind of telling me its on the way out and it's our supposed Summer so have time to sort before it lets me down on a cold morning.

 

[Agile]

Are you sure that its doing this when there is a demand for heat?

And its not just the pump over run and you dont have an auto bypass?

Tony

 

[Wictod]

No, it's not doing it when there's a demand for heat, it only does it when the gas is off and the pump is still circulating before it stops, like a random clattering. Once the burner stops it runs for about a minute or so before stopping completely.

 

[Wictod]

From the end of a screwdriver it sounds more prominent from the black box part that sits on top of the grey metal pump housing.. Not sure what this part of the assembly does but looks like its where the power cable feeds the pump?

 

[mickyg]

its probably doing it when the pump speed drops. its a 2 speed fan. for hot water and for much of the heating cycle it will prob be on max speed, for overrun it slows down hence the difference

 

[Wictod]

ok, that makes sense, so I guess the high speed is masking the issue which is clearly evident at the slower over run. I presume it's still on the way out then? btw, thanks for all the replys for members, nice to get some understanding of the issue, been bugging me for a while.

 

[Agile]

Do you have motor valves or all TRVs?

 

[Wictod]

if you mean on the rads i've got TRVs but most of them are off because they're a pain.

 

[The831Bunny]

Its the pump, end of!

Next symptoms are it will leak I'm sorry to say.

I'll raise you mickyg and I'll give it two months...

 

[Wictod]

831, There's some evidence of a leak underneath the pump area, so i don't know whether it expelled water and sort of sealed itself because it's dry at the moment.

 

[Wictod]

Changed the pump out today for a new Vaillant / Grundfos model. The old pump didn't look too bad but had a little lateral play in it but no side to side movement from the bearings. Was a big blob of limescale in one of the impellor water ways as well. When I removed the old assembley the lower diverter valve hole (smaller one) was full of black crud even after i'd flush it with cleaner. Was also the same crap in the diverter valve. Some more black crud in the canoe filter but couldn't get the damn thing out. Anyway all put back together and no knocking noises and overall it's noticably quieter so happy with the afternoons work. Thought i'd better get it done before Winter arrives..