Your right, I didn't have to drain it all. But, since I replaced all the other fluids and I don't know when the coolant was, or ever changed, I decided just to let it all come out. I didn't look bad, but I already bought the new fluid, so I figured what the heck. I'll have to look into how long before I need to replace it again. Otherwise, next time I need to pull the plenum, I'll only drain the top out.
