The very first thing you need to do is shut off the boiler and let it cool down. Oh yeah, it’s about 190 degrees on the inside!
After you let it cool down it’s time to remove the chimney / flue pipe.
This is what you don’t want to see. But hey, that’s why you’re reading
this, right? Now just get a good strong vacuum and vacuum that junk out.
This will help see just how bad it really is. A boiler is made up of sections (cast iron) with nubs on each side creating a nice cap for the flame / heat to pass through. This heats up the sections and the water inside these sections.
As you can see from the above picture, in some cases these sections can get packed solid with soot. At that point, it’s just a matter of lots of hard work to clean it out.
In the above picture, I’m a running a very special steel brush (available at most plumbing supply stores) from the top straight down through the bottom into the fire box. Even if it looks clear, I want to make sure it is. The cleaner the better! I don’t want to do it again anytime soon.
Now it’s time to remove the burner part. Yes, this is what makes the flame. Make sure all power is off. Do whatever you have to do at any point when working on a boiler when the power is off.
From the above picture, you can see three threaded studs. Most newer boilers will have three nuts that hold the burner on. Just remove these. Take notice of the gasket. Most of the time, you’ll need to replace this. The gasket is white and round. This goes against the section burner. Also, if your fuel line is flexible enough you can just lay the burner on the floor. Otherwise, you’ll need to disconnect and plug the line before you start.
Now look at that, and there’s a lot more inside! Inside here, you’ll notice the firebox is lined with a white padding. This is very special stuff; it’s soft stuff that, over time, may begin to look like steel. It’s okay if it looks like steel, as long as it in place. If you don’t have it, just go to a plumbing supply house get some. This prevents the flame from hitting this section directly.
Now, use a strong vacuum to clean the inside, but be careful not to suck the lining up. I just placed my hand over the vacuum hose to control the suction better.
Once you’re all done cleaning and inspecting your boiler, the rest is as easy as putting everything back together and firing it back up. You do need to have some knowledge of a boiler before attempting this. If you don’t, just call a pro and watch him for the first time.