I have a 1983 Bryant gas boiler (235 model), radiator set-up. I noticed a drip this season, in the front. I pulled the front cover and about
2/3 the way up, on the right front, is this square plate, about 1 1/2" square. There is a small threaded rod sticking out that turns but does not tighten up. It is dripping from this. What is it? It is not a blow off valve, that is on top. Thanks in advance! David