I had my boiler inspected and cleaned recently and the tech found a few issues. He showed me how the valve on the expansion tank would leak when he would push it in, which means the tank needs to be replaced. He also showed me how there was water leaking out of the Taco air vent. Later when I inspected it on my own, I couldn't feel any water leaking from it. With the system off, should there still be water leaking? I am just trying to get a better understanding of the system and what needs to be done.
They were charging around $800 to replace the tank, vent and to drain/fill the system. We have a lot of noise in our pipes, so I assume air is getting in some place. Could it be either of these two places if they are indeed leaking?