One of my hydros is leaking oil. It is the left hydro. I noticed a good bit of oil in the area around the hydro fan. I can't see a crack in the reservoir. I can only assume that it is coming out of the seal around the shaft. Can these seals be replaced? Any other likely place where it might be leaking fluid? The unit still seems to work good as long as the fluid leve is proper, so air doesn't enter.