I did this job earlier this week.

I used a sealant from FastLane called, I believe, Curil. It was in a tube with German writing all over. It was black and looked and smelled exactly like some old Permatex gasket stuff I've used in the past.

Oh, and no leaks.

And, I installed the new camshaft seal AFTER the cover was in place. Seemed safer to do it that way.

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2012 E350
2006 Callaway SC560