When my pump was seeping a bit of oil and coolant back and forth - Joel W. told me that the coolant is sealed inside that unit by two discs back to back. No service can be done. Don't those o rings replaced in this DIY just seal the unit in the bike?
He said the back to back discs sealed the coolant, and may seep from time to time under the right circumstances, but last a long time. The oil is a o ring seal, but again - inside the unit.