Yup, that was the source of the oil in my coolant. In the pantheon of things that can cause something like that, that was the least bad, but probably most common! PS: If you decide to do this yourself, keep very good track of which o ring goes where. As noted in the thread, they look almost identical to the naked eye once they are outside of their numbered envelope but they are not and switching them in position will not solve the problem. Ask me how I know!
