I just did this on my 85.

I cleaned the seperator out really well. Bent the tabs up and cleaned all that up. and put the lid back on with some RTV around the edge. I also replaced the O-rings on the drain: One where the air cleaner meets the pipe and one where the pipe meets the oil pan.

I did not have anything inside the seperator itself though. Is there supposed to be something in there?

One thing I did read after the fact is that there is a check valve near the oil pan, I did not check that and will next time I have everything apart.

I still get leaks around the "nipple" on the valve cover that goes to the air/oil seperator. I really wish I could fix that. I have some blowby as well, but it is not bad at all. I have seen much worse.

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----Adam

1985 300SD 322,000