its actualy the suction tube mounting flange .with the pump mounted on the block it would be the lower hole .the material around the bolt hole is barly 3/16 thick . i can clearly see a crack in the midle of the small piece the came off and i am wondering if it happend when it was threaded at the factory? it looks like an expansion crack. the other bolt hole has a lot more material around it. still waiting on a new pump but i will be looking at it with a magnifying glass thats for sure.