copper tube boiler quiet now (knock on wood)

Dave_61

Hey Guys,
I had posted this past week about our copper tube boiler, which had been silent since its repipe job this past winter. Then it started this rumbling/percolating sound when the gas burner would come on, sounding like an old oil burner in the main living space of the house. We have a 30% glycol/water mix. Some thoughts on the Wall were that we had scale or other contaminants, or that the flow was too low. Among other things that I noticed, the T&P gauge on the inlet was malfunctioning, showing a higher inlet than outlet temp. Also, the pressure needle would vibrate when the burner was on.

I have no clue, but the noise has stopped completely......Here's what i did.

I closed the valves to isolate the boiler and relieved the pressure. I replaced the bad T&P gauge and then let some more water run through the boiler before recharging the system and restarting it.

It is completely silent again.

And I closed the boiler outflow valve about 10%. The DDT reads between 20-25. (max is 40 per manufacturer.).
Any ideas why the sound would have gone away?
Only time will tell whether it comes back.
The pressure needle on the new inlet gauge does move back and forth a little but not vibrating like the old one did. Is that normal to see a few psi of movement?

I will be making a donation to the Wall for all your input.
Thanks.
Dave