GMC Other Repair Question
I hate to be the bearer of bad news but what you have described is classic symptoms of a bad head gasket. I don't see where the water pump has anything to do with it unless now that the water is circulating the bad head gasket it showing itself.
Not sure if v-6 water pump has a way of leaking into oil, it sure sounds alot like a head gasket.Does your water keep going down in radiator? Does the motor seem weaker than it used to be? Run a little hotter than normal? All indications that is what you got.
2 questions asked