Novice on this trying to make sure I have it right to fix the gurgling/banging. I'm not completely clear on terminology

A) At chest level there are two valves with hose bibs on parallel pipes heading down (assume those are the two zones).
B) Below each of these valves are another valves (assume the gate valve). Pipes merge under these valves.
C) I think I found the quick fill brass lever on the narrower perpendicular pipe to the others mentionsed above that sounds like it infused water when I tested it.

After turning off the unit, do I bleed each zone seperately? e.g.

1) Connect hose to upper bib valve
2) Close gate valve
3) Open bib valve
4) Drain a gallon or two while ?simultaneously? activating quick fill? Or do I drain, then close bib valve, then quick fill, then open gate?

Basically I'm trying to get the sequence right.

 

Before you do anything, it's best to determine WHY you have so much air in the system. You might spend a lot of time trying to get it all out and then only have it come back a week later...

so, first things first... read the temperature and pressure gauge on the boiler and tell us what it says.

For us to best help, it would be good if you could take pictures and post them to a free account at Image hosting, free photo sharing & video sharing at Photobucket and provide a link for us to view the pics. Take a few from a distance back and several angles so we can make sense of the pics.

 

Looks like Temp is 160 deg; pressure 18 - 20 PSI

Burnham Heating System pictures by hijump - Photobucket

4 pics - entire front; guage and two side shots.

 

Just revisiting this to see if I can get an assist. After re-looking at my sequence I think I may have to:

After turning off the unit, do I bleed each zone seperately? e.g.

1) Connect hose to upper bib valve
2) Close gate valve
3) Open bib valve
4) Drain a gallon or two while ?simultaneously? activating quick fill? (until it runs cleanly) Or do I
4a) Drain a gallon or two, then close bib valve, then open the gate; then quick fill?
5) And repeat with other zone?

Basically I'm trying to get the sequence right but knowing root cause I guess would be good. It's less about trickling noise and more about the pipes "banging" periodically.

 

That's the basic idea for bleeding - (but see my general questions at the end of this post.)

First, cool down the boiler to 100 deg or below.

Then open the manual valve upstream of the backflow preventer and automatic fill valve. That should add water automatically as you drain it. If the pressure drops to less than 12 psi, you can go ahead and lift the fast-fill lever to restore the pressure.

Do one bib at a time. Yes, shut the "gate" valve in line with the bib. (I'm not real sure they are gate valves, but whatever.)

Use a short piece of hose into a bucket with a couple of inches of water - that will let you check for air bubbles. Don't worry about the water running "clean" - there will likely be harmless black stuff in the water which you needn't worry about. You want to minimize the amount of purging, because the make-up water brought in will have lots of disolved/retained air in it.

I see the copper-colored air removal device in the lower-right of Pix 2. I can't tell for sure - is the valve cap on top screwed down tight? If so, remove it or loosen it so air can escape - that might be part of your air problem.

Has the system recently been opened for maintenance? That can bring air into the system.

Normally, air should not get into a properly operating system, and even if it does, it makes me wonder why it isn't being automatically removed by the air removal device. So, besides bleeding the air, two questions need to be resolved: 1) how is air getting into the system, and 2) why isn't the air-removal device working? Bleeding the air without answering those questions might not solve anything - bleeding will bring in more air with the make-up water.

Gurgling noise can be caused by air. And air can block flow. But usually air doesn't cause "banging," but I guess anything is possible. Banging is usually caused by thermal expansion or contraction of pipes, particularly where then touch wooden joists, etc.