Zimm

I have a few issues i need help with - 1st its a 89 rx7 vert non turbo, and the top of the rad was cracked so previous owner jb welded it and fixed it for a while then a month ago the jb weld blew appart or whatever happened so it leaked a bit for a bit and i jb welded it back up the other night then i was driving it and it blew a hole in another spot on the rad and there was a **** ton of pressure in the rad and it wasnt even over heating, the only thing the temp did was go to 3/4 when it had all that pressure, think its just my rad clogging somewhere if so where good place to get a rad??

Also when its cold it runs rough previous owner told me what it was, said you just have to clean the sensor or something anyone help me with this whats the best way to fix it??

Thanks