Thank you for letting me partake. I know nothing about anything and less about boilers. I have a small apt. with a Weil McClain boiler. it was making a crazy sound so I shut the power. when I turned it back on I realized it was the recirculation pump making the racket (TAKO 007-F5). I also noticed a drip from the expansion tank. I replaced the recirculation pump. BUT. I noticed no residual water coming out. I turned the system back on and after 1/2 hour the new bump was burning hot. I guess there was no water to cool it. PLEASE HELP.