93 323 overheating

hi all, new member here,my daughters 323 is overheating and im thinking its the core (freeze) plugs.there is coolant (steam?)coming from underneath the heat shield but i cant see exactly where.i dont think its a cracked block-no "chocolate milk" in the crankcase,could be a head gasket but cant tell,i hope not !.the previous owner used H20 in the cooling system.(ugh) .when i did a drain and flush,lots of rust particles along with rusty water ,came out so im thinking a freeze plug was weak and rusted.and with the pressure build up its just let go.so my question is where are the freeze plugs located and can they be changed without pulling the motor ?.thanks,

hI, iS THERE ALOT OF PRESSURE IN THE COOLING SYSTEM LIKE BUBbLES EXCESSIVE AMOUNTS?

Would be best to pressure test the cooling system and get an eyeball under that heat shield or better yet remove it.