Possible Cause of CH Pump Noise on New Boiler?

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My mother had a new gas condensing conventional boiler fitted in mid-December (Worcester Greenstar), replacing an ancient Baxi. The pump (a Grundfos) was reused from the original system as it appeared to be in good condition and was only about 5 years old. Have just visited her and found that the pump is making a very light rattling noise when it cuts in, best described as like small ball bearings in a tin...she is very deaf so simply hadn't noticed it. It's definitely the pump, as when I turn it down to the lowest speed the noise almost vanishes, when I turn it up to highest the noise is worse.
The system was chemically flushed when they changed the boiler, could this be a bit of debris dislodged and now trapped in the pump, or is it indicative of pump failure?
If it's the former, are the installers likely to accept responsibility and clear/clean the pump at their expense? We were not advised either to leave the pump or to change it, they just reinstalled the old one without raising the issue.
I'm going to call them to discuss but just a little unsure of where we stand on this and what the problem might be.
 
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Pump noise is related to either air in the system or pump failure. Air in the system will be pumped into the radiators within a matter of minutes, meaning the pump will run silently. Therefore the pump is starting to fail, and a replacement pump will be required in the near future.
 
The noise is continuous, it is present from start up all the time the pump is running. It doesn't sound like bearing failure to me, too light, more like a car engine pinking under load.
I should have added that since the boiler change, there has been some air in the system, she has bled the two highest rads about twice a week, we were advised that this was normal with a new boiler and should diminish in a few weeks.
 
Sounds like small particles of solder in the pump. Should be easily removed by shutting the isolating valves and taking the pump head off.
 
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Thanks, yes that's exactly what it sounds like. So basically this is down to the installers not flushing the pipework thoroughly before refilling the system?
I can't believe the pump is starting to fail, as it was completely silent with the old boiler, and the coincidence is just too great.
 
Not necessarily, a flush may well have pushed the solder up into the pump. They should still be willing to come back and sort the problem though.
 
Update: got the engineer back and he stripped the pump. No debris in it and water running clean. He says one of the bearings is probably starting to fail and has changed the pump (at our expense obviously).
He reckons that because it was mounted horizontally behind the old boiler and now vertically below the new one, we are hearing a rattling that may have been there before, or that changing the pump angle has made the vibration noticeable.
Is this a reasonable diagnosis or am I getting a whiff of red herrings?
As mentioned in my earlier post, the pump is not more than about 6 years old, I am told that Grundfos are usually good for 10 or more.
 
He may well be right.

If the water was runnign clean and he has changed the pump head and it isn't making any noise now, he has solved your problem :p
 

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