Every DSM owner knows that it is nearly impossible to keep the turbo oil return line from leaking at the oil pan.

There is an easy fix for this, if you already have your oil pan off or don't mind removing it.

The Theory:
Even when you apply a good sealant on the stock gasket between the oil pan and oil return line flange, oil still finds it's way out. Part of the problem is that you do NOT want to put too much sealant on the gasket because it could possibly clog up the oil line. At the same time the oil return line has a radius where the oil tube is welded to the flange. I feel this radius creates a gap that allows oil to work it's way between the sealant and the gasket or flanges.

The Procedure:
To be able to fill in the gap, you need to get to the inside of the oil line. Unfortunately that means the oil pan must be off of the engine. I would also recommend using GM sealant because this stuff is the toughest sealant I've ever found.

Clean all mating surfaces with 'brake clean' or something similar to remove all dirt, oil residue, old gasket material etc. Go ahead and and mount the the oil return line to the oil pan like normal with the factory gasket and the GM sealant. Then turn the oil pan so you can access the line from inside the oil pan. Apply a small amount of sealant inside the oil line and smooth it out so that all the gaps are filled in. The optimum result will be to have a thin film that traverses all gaps to keep oil from sitting in them.

Once you have this complete you can mount the oil pan to the engine. If the turbo is already mounted to the engine you will have to pay attention to both the oil pan sealing surface and the upper flange on the oil return line. Again I highly recommend using the GM sealant.

Finish assembly like normal and enjoy a dry oil return line. See the attached picture for reference. This is a view of smoothed out sealant over the oil return line mating gaps as viewed from inside the oil pan.

The problems I had with my return line never was with mating it to the pan. It was having a faulty "flex" section of the line.

The repair I recommend for that is to remove that section and install a piece of flexible tubing.

You did have that issue with the flex section, but to be honest I don't know if I personally ever seen anyone else with that problem. I think you had some bad luck for sure on that return line or two. In most cases we need to cut out the old flex section and use a hose to help make a larger turbo work anyway, so I agree with your recomendation.

The reason for this tech thread is based on the number of DSM's I've had and especially seen when at Slo Pny, that ALL had the oil leak from the oil return line flange at the oil pan.

We tried a number of things to cure this and very rarely would anything work. That is untill I tried this more thorough process of making sure the gaps between the oil pan and flange are totally sealed. It seems simple, but it took six years for me to think it through and go through the process. This process was finally used on my stroker engine the lsat time I put it together. It was dry as a bone the entire time...even after the #3 rod tore the middle out of the oil pan.