What I can remember about the bottom O-ring on the tube is different the what others have said. To me it appeared that the bottom of the Tube and therefore the O-ring had to be pulled up inside of the Grommet. And, if I remember correctly there is a groove inside of the Grommet to accommodate the O-ring.

Best to take a look at the relationship by seeing that relationship before you install the grommet into the block.

However, I am not sure of my memory on that.

I do know that it worked out way better pushing the lower turbo drain tube up from the oil pan side with a socket and in my case I gently used a bottle type hydraulic jack.

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84 300D, 82 Volvo 244Gl Diesel