PLEASE HELP W/ Leaky air vent and banging too! Maid-oMist

The Harts

I have no idea about steam heat. Please bear with me!!! I have a leaky baseboard. I removed the end cap where the air vent is, and noticed that the leaking seems to be coming from a maid-o-mist. Is this a air vent? It looks Like a two piece fitting one part threads into the end of the pipe, and the other cap is cripmed on with what looks like a round vent on it. Sould the round vent be facing up? This is where its leaking from. Also, the thing hisses constantly. We also have major hammering when the heat first starts, but it is only in the one line to the furtherst radiator from the boiler. All the others are pretty much quiet except for what I think is hissing air vents. How do I fix this?!?! Can I make repairs with the system running or should I wait or shut the boiler down? This is our heat and hot water provider. We also have to refill the boiler every other day since winter has started (granted the heat has been on non-stop). Will I induce air into the system if I removed the Maid-o-mist? Will this cause even more banging?

Steamhead

I'll bet

the problem is with the way the baseboard is piped. If this is fin-tube baseboard, it will never work right when connected the same as a one-pipe cast-iron radiator. It must have a return line, otherwise water will be held up in the baseboard and cause the banging, which is sure to kill the vent.

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The Harts

A more clear description

I wasn't clear enough in my posting though. The one that is leaking is not the same as the one that is banging. The one that is leaking is in the bedroom. We two types of heaters in the hose, the old metal radiators and the one that is leaking;the baseboard type. The baseboards were added almost 50 years ago, and as far as we know there hasn't been any trouble. The baseboard that is leaking has a pipe coming straight from the boiler into the baseboard heater and ends there. At the end there is some type of valve. As I described in my posting I removed the end cap where the air vent is, and noticed that the leaking seems to be coming from a maid-of-mist. Is this a air vent or a steam vent? It looks Like a two piece fitting one part threads into the end of the pipe, and the other cap is crimped on with what looks like a round vent on it. Should the round vent be facing up? It is leaking from where the cap is crimped on. Also, the thing hisses constantly. Do you know what this might be? All of our radiators don't have returns. Only the one in the living room (which bangs) has a return line back to the main pipes (is this the end of the loop?) I wonder why it's acting up now after all these years?

scrook_2

Maid-O-Mist

That's an air vent and the orifice should point up. It should vent air (maybe w/ a hissing sound) then shut to steam (maybe w/ a click), and may reopen and close from time to time. They do get crudded up w/ minerals and leak steam sometimes, boiling them in vinegar *sometimes* will clean them, otherwise they need to be replaced, but are not expensive. Hoffmann, Gorton & Dole are other brands of steam radiator air vents (though people may call them "steam vents").

You might try buying a new vent at a local hardware store, turn down the thermostat, let the radiator (baseboard) cool a bit, screw out the old and in the new and turn the t-stat back up.

The banging radiator may be trapping condensed water for a number of reasons: it may have shifted so it (or its pipe) is no longer pitched down, or the valve may have become partly closed (full open or full shut only for 1 pipe steam!) or th evalve washer may have come loose, or something else.