FWIW, My In-Law's 130 year old house has steam heat, my late father in law used to run Lye thru the system a couple times a year to clean it out and keep it clean, that was how they always cleaned out steam systems back in the day, something nobody seems to know anything about nowadays.
The old boiler lasted the 55 years that he was alive in the house and was probably installed in the 1910's or 20's.
Installed a new boiler 16 years ago shortly after he passed away and now I get stuck doing the lye cycling for my 98 year old MIL. lol
Somewhere along the return line there should be a fitting or plug, find that, shut your boiler, then drain the entire boiler, remove the plug (you may have to heat it up with a propane torch to get it loose!), mix lye in a gallon of warm water to dissolve it (you can buy lye at any hardware store or home improvement store, some plumbing supply houses stock it for this purpose, use a funnel to pour the water with lye in, refill the system the rest of the way back to it's normal water level, then run the system for at least an hour, just so that the lye has time to circulate thru as much as it can, shut system, let it all drain back into the boiler for at least 1 hour and cool off, then drain boiler again, than refill the boiler again, repeat with another bucket of lye if the water was really dark orange and heavily rusted and repeat as many as three or four times.
Here's another free tip that I learned with steam heating;
You should NEVER shut ANY radiator shut off valves in a steam system, or else the pressure can build up in the pipe leading to that radiator and cause a pipe or connection or fitting to burst, which always makes me wonder WHY do they even put shut off valves on steam radiators and not just a union to connect them?
And another free tip that I also learned;
The little steam valves should always be on the opposite side from the side the shut off valve is installed and the side with the shut off vale SHOULD be slightly higher than the side with the steam valve and the steam valve should be cleaned every year or two, if they get blocked with dust that can fail to let heat rise, because the air can't escape and you end up with cold rads.
I have also read that you can take a steam valve off, blow in it's threaded end and if nothing comes out it's air hole, it's obviously clogged.
You can try to unclog it with a needle, or if that doesn't work, by boiling it in a pot of 1 cup of water with one cup of vinegar and a teaspoon of salt and letting it boil for at least 20 mins., remove from pot, allow it to cool off and than try blowing thru it's threaded end again. You can boil more than one at a time if need be.
If air comes out, it's clean, reinstall it, if not you have to replace it, use a thread compound intended for steam heating/steam rads, plumbers tape will most likely melt and some compounds will give off terrible fumes if used on steam rads.
There are different steam valves for different locations in a house or building, it depends upon how far a rad from the boiler or how many flights up it is.
There used to be a few charts online for reference, you can probably google "Steam Valve Locations", or something to that effect to find a good one, but i will provide a link for one chart I just found.
BTW, Maid 0 Mist seem to be everyone's go to brand for steam valves over the cheap chinese ones.
I have a single pipe steam heat system with radiators. To use this system I use the Maid-o-Mist brand valves. These valves come in different sizes. The website provides a nice diagram about what
diy.stackexchange.com
Just to keep the system clean, once a week I go down to the cellar and drain at least 1 or 2 gallons out of the upper valve on the side of the boiler to "skim" off the top, and than another gallon or two from the bottom drain valve until any rusty/dirty water stops coming out, than I refill it and dump the bucket.
If you still don't get heat to the rads you said don't heat up, you might have to disconnect each rad, remove the shut off valve (which shouldn't be closed) at each rad, pour lye right down the pipe from each location and flush them out with a bucket of lye that way, but I've also heard of guy's using a bicycle pump at each rad to use air pressure to force a clog out, but you have to drain the entire system and leave valves open to blow the junk out.
Also, inspect where each pipe goes up towards each radiator if possible and make sure you don't see any water coming down any transoms where a pipe is.
We had a leak in a wall where an old connector for two pipes going to the second floor rotted thru, what a hassle it was to open the wall, remove the pipe from the rad's shut off valve, remove the leaky connector and I replaced it with a union, just in case I ever have to go back into that wall again and than patch the hole up, sand, prime and paint the wall.
Took me a day and a half.
Good luck!
