I was installing the 2 gen. bracket bolts that go into the eng. block and they were going in hard.  They are 5/16-18.  They look gauled but I'm sure they are 5/16-18.  Anyway i'll replace them just to be sure.  My question is when I stuck an awl into both holes to measure the bolt length, the upper hole has a solid hard bottom to it but the lower hole was soft so I pushed the awl in and antifreeze water came pouring out .  Is this normal that the lower bolt goes into the water jacket and the upper one does not or did I punch through some rust?  The water was clean and rust free.  Any thoughts?
Thanks, Charlie