go bad
     v 1: stop operating or functioning; "the engine finally went";
          "the car died on the road"; "the bus we travelled in
          broke down on the way to town"; "the coffee maker
          broke"; "the engine failed on the way to town"; "her
          eyesight went after the accident" syn: fail, give
          way, die, give out, conk out, go, break, break
          down
     2: become unfit for consumption or use; "the meat must be eaten
        before it spoils" syn: spoil
see also:
fail give way die give out conk out go 
break break down spoil