Noise has returned?

[darren6645]

I was getting a noise when the boiler was on full flame, initial start up until temp setting was reached or if high demand, shower running heating on. It sounded worse if I slowed the circulation pump down and slightly better when I turned it up, sounded like a rumbling but only when on full flame.
After posting on the forum I had lots of helpful advice. I proceeded to drain my system, fit a new magnetic filter, refill the system and dose with sentinel x400 x4 which I circulated for 2 weeks, cleaning filter periodically. I then drained the system completely again, refilled and drained a further 4 times before fitting a new grundfos ups3 circulation pump, refilling and dosing with inhibitor x4 and noise reducer x4. System had been almost silent since 17th Feb but last night I noticed a slight rumble again when on full flame?
Any ideas, I don't understand how it's been perfect since I've done the work and now started agai ? The only thing I've done last couple of days was flush magnetic filter?

(I have a 180l flowmax thermal store, vaillant ecotec plus 418 boiler 7yrs old and 19 rads, water is red hot, radiators are hot top and bottom, two grundfos circulation pumps, one circulating from store to boiler abs back and another circulating around rads when required)

 

[Bodd]

X 400 will just aggravate and mobolise the sludge. You won't get it all out.. eventually it will clog the pump and maybe the heat exchanger

You need a Kamco Powerflush

 

[darren6645]

X 400 will just aggravate and mobolise the sludge. You won't get it all out.. eventually it will clog the pump and maybe the heat exchanger

You need a Kamco Powerflush

I don't think I had a sludge problem, I had no issues with cold spots in rads and system flush wasn't really dirty but as I was doing the work I put it in for the required period.
I have micro bore on my heating side so powerflush not recommended. System has always had inhibitor added, boiler serviced annually along with magnaclean and combi mate fitted from start boiler is only 7yrs old, but thanks for the reply.

 

[durhamplumber]

You need a Kamco Powerflush

Like you need a hole in the head

 

[Bodd]

Like you need a hole in the head

Rightly so if it's microbore.

Is that your objection to powerflushing or is there another

 

[Bodd]

I have micro bore on my heating side so powerflush not recommended.

Yes I don't like powerflushing microbore.
Best avoided if there is a better solution.
Saying that I have in the past. I went about it in a diffrent way. Flushing through 2 or 3 Rads at a time instead of one.

 

[Terrywookfit]

Yes I don't like powerflushing microbore.
Best avoided if the is a better solution.
Saying that I have in the past. I went obount it in a diffrent way. Flushing through 2 or 3 Rads at a time instead of one.

The main problem with flushing microbore is not enough volume to mobilize the $ hite.

 

[darren6645]

My ground floor rads are on drop downs (I think that's the correct terminology) so I drained each rad individually each time I drained so they all had a good flush out.
The noise is literally only there when the boiler is on max flame once flame reduces it goes instantly?