Sorry yes after rereading your post I got where your problem is.

Actually while flushing my (temporary) turbo replacement I found that the flow through that bearing was not a simple pour it in pour it out thing even with kerosene. I think there is a certain amount of restriction in the bearing but you are right once it has passed thru the bearing it should flow down the tube and back into the oil sump wihtout pressure unless the oil sump is being affected by excesive pressure in the crankcase.

I used some high temp rtv on my flange (with a new gasket) and it did not leak. Could the mating sufaces have gotten scored or perhaps the flange on the return tube gotten bent slightly?

I learned a trick to removing the tube with the turbo in place. I took my dremel and ground off about a 1/4 inch of the tube "bell" where it slips over the lower tube. This allows you to pull it loose without removing the turbo much, much easier.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique