I recently did head gaskets on my 87 gl wagon because i was getting oil in the coolant. I bought a regasket kit for the top and bottom end and have been replacing lots of things. Although, i noticed in my hanes there is a "crankshaft o ring" and "backup ring" right where the block splits. I read a service manual online and it called it a coolant passage o ring. I was wondering if anyone knew if these go out very often and if they do can it cause oil in the coolant? I really don't want to redo my head gaskets