Two downstairs rads not working

Hi Everyone

Tearing my hair out as I have been struggling with this prob since before Christmas!!

The rad in the hallway failed gradually, ie gradually became less warm each time the heating came on over several days until it refused to heat up at all. I bled it and there was no air in the top of the rad, so I had a plumber vent the rad from the bottom and black sludge came out and trapped air. It worked for a few days but then failed again.

In parallel I had an additional rad fitted to some existing pipes that had been sealed off by the previous home owner. The same plumber drained the system and refilled it. There did not seem to be any corrosion and the sludge seems to have gone. The plumber really struggled though to get all rads heating up properly, but eventually he succeeded.

BUT - The same two rads failed gradually again over the next couple of days. Twice now he has vented both rads and removed more air, got the rads working and then they have failed again. The system is a sealed version and he is at a loss as to where the air can be coming in from and I only have a total of 8 rads on the system inc the new one.

Any ideas?

I should also mention that when the CH comes on there is a lot of gurgling noise from the boiler which settles down in a few minutes.

L

A sealed system? A combi boiler, perhaps?
Either way the presence of sludge in your system does not bode well.

My recommendations are to flush the entire system to remove the sludge, then manually check the pump is clear of debris (impellors block easily), then treat with corrosion inhibitor to complete the job.

Thanks for the swift reply!

It is a combi boiler - a Ferroli - but I don't know how old it is.

Since the first batch of sludge was vented the first time the plumber arrived the water has run clear and each subsequent occasion that he has vented the two duff rads.

The plumber I am using suggested a full flush, but it seemed an expensive exercise and I was unconvinced as to whether it would fix the problem. Now that you've given a second opinion I'll think about it again.

Any comments on the gurgling that then disappears after a few minutes?

L