I want to drain and flush until clean but the PO tried that and I don't think did a good job. I'm told if I don't drain from the right places, crud won't flush out. Trying to learn the best way to do it. The crack allows air to enter the cooling system on these. I suppose it could go into the oil, but it's not and I'm told this is common on DD 92s. Just the way it goes, I guess. Still cheaper than some other things. My buddy has to do a service on his IPS drives and he will pay the marina almost as much as a head job will cost me (doing it with my own mechanic)!