I will be replacing my oil pump without removing the timing cover from my 1985 4Runner. I know placement of the o-ring is critical to get right (no pinches, etc), and doing this with the timing cover still on increases the chances of that happening. I've seen some people use vaseline, lithium grease, assembly lube, etc to coat the o-ring to keep it in place. But then I saw a YouTube video by Yota1 where they coat the o-ring in grey RTV. So not only does it hold the o-ring in place, but potentially can serve as an extra "gasket" layer to help that from leaking down the road.

Has anyone else done this, and how have the results been over time? My concern here would be given the thickness, perhaps it won't seal properly. Also, there is the possibility of RTV shedding off into the oil system.

 

While I'm sure that it would work, it seems like a bit of a hackjob to me. The surfaces should be clean and the O-ring new or very close to new if re-used. Grease the slot in the timing cover then install the O-ring. I've never had a leak with this procedure. RTV would just make a big mess that you have to deal with next time you take it apart.