He means the head gasket. not uncommon up hear, negitve bloody cold + not plugging in the block heater can = cracked water jacket or head gasket or frozen lower rad hose is a good one that means that you WILL over heat even at -20 or 30 which will give you a cracked head or head gasket.
Don't ask, I do know this is fact as stupid as it sounds.
My pos DD
90XJ Laredo 4.0L(now HO) Auto, 6.5"lift, 36"x12.5"SSR's, custom this and that (snorkle, rockers, bumpers, etct), winch, lights, more crap to come.
90XJ Ltd Up Country, Bored and stroked 4.7L I6 Auto,
2.5" lift 31x10.5"Hankook AT's.