Looks like a crack to me and it's right at the bottom of the water jacket where they always crack. It might have a pile of rust sediment behind it sealing it from leaking.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD
