OK I have a two story building and with the hot water off the pipes are going crazy with shaking,if I cut the hot water on it stops.I have replaced the expansion tank and that did no good. I also have a circulating pump running in the system. I have no silinoids except an ice machine anywhere in the system. There is nothing causing backflow on any faucet.ok now what

" the hot water off the pipes are going crazy " this tells me that there is water still moving through the system and passing through a valve somewhere. Close off all faicets, get the pipes to vibrate and them take a close look at your leak detector on your water meter, it's the little V shped pointer in the middle, does it move with everything closed