I was removing my rocker arm shaft to check for wear on the rocker ends. After removing the #2 rocker pillar bolt, engine coolant geysered up through the hole. Never had this happen before. Engine is B-18 with a _AG code head. PO had unleaded valves and seats installed, as well as porting and cc polishing. Any clues before I pull the head? Like I said, in 37 years of working on these engines I've never see this. I thought that the rocker pillar thread holes were blind, save for #3 hole with the oil feed for the rockers. Thanks!