I've got the oil bath hubs with the aluminum cap and sight window, took the allen screw out and drained the first one for my annual change this weekend and now I am having problems getting new oil to show in the sight window, filled it as much as I could and definitely had some go in, maybe not as much that came out but I'm not seeing it. Let it sit awhile and still nothing, guesssing there may be air in there, any way to get it out? If a little water got in would that cause problems with getting oil back in it, oil that came out wasn't milkly though, it was black.