Question about bleeding baseboard heating

Question

I have a house built in 1949 with baseboard heating (5 loops), and I don't seem to be able to find any bleeder valves at the baseboards themselves. One of the loops in particular is making an awful racket. I've watched a few videos on how to bleed this kind of system (with a hose), but I'm not clear on how to do that with my setup.

As far as I can tell, each of the baseboard loops only has a shut off valve on the return side. One of the five does have a valve on the feed side, but that's not the loop that's making all the noise.

I have pictures below that could help, but in terms of the general process, is it as follows?

1. Shut off the boiler
2. Close all the valves on the return side of the loops
3. Attach a hose to the spigot on the return-side
4. Open one of the 5 return side valves
5. Presumably at this point water (and air) flow out through the hose, but perhaps I need to open the feeder valve now too? I'm not sure if I should expect the system to regulate the water pressure itself in any way...
6. Once I have only water coming from those hose, shut the hose spigot and then the baseboard loop return.
7. Repeat 4-6 for the other noisy baseboard loops

If the above is accurate, I'm looking for A. some clarity on whether I've properly identified the spigot I should be draining from in the pictures below and B. input on how to fill the system using the feeder valve (i.e. do I shut off the spigot BEFORE I close the feeder? Do I have to worry about monitoring the system pressure as I do this? Etc.)

Thanks in advance!

-Jack

Here are the pictures showing the setup (I did my best, parts of the system are sitting between duct work so pictures were a bit tough...and forgive any imprecise naming of things, I took an amateur stab at it :) ).

I'm assuming the spigot labeled in the picture below is where I should drain the system?

For the sake of completeness, it's a two-zone system with a radiant floor loop, but I'm ignoring that here.

This picture reflects the nightmare that is all this stuff tucked between the ducting, the subsequent pictures might make it more clear.

There does appear (I think?) to be a bleeder valve for the whole system atop the compression tank, it's wide open on the thumb-screw on top

Same as above from the other side for clarity.

Here's the baseboard zone, post-compression-tank showing the run through the circulator, flo-chek, and split to the 5 baseboard loops

And finally here's the return from the baseboard loops showing the shut-off valves.

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Regarding Freeman's comment, I'm challenged to find the pin mentioned. Best I can tell that bleeder just has a thumbscrew, and even when I take it all the way off there's just plastic threading (see below). Am I being dense?

Answer 1

So you found the "Bleeder" valve, congratulation.

It is missing the cap (or removed), and the question is is it still working or stuck.

Sometimes after long use there is enough dirt in the Bleeder to make the floater inside get stuck in the upper position ,and is no longer bleeding the air.

Here is the cross section of the bleeder valve with floater inside.

Simple test if bleeder is working...

Attach a balloon to the top. See if it blows up. It might pop if too much air. If nothing happens the bleeder is not working.

Simplest solution is to replace the Bleeder valve.