If this is the vehicle you Have : I have a 77 240D W123 Automatic." is Engine 617.912.

That needs a reamer with 18mm threads and that reamer is harder to find and more expensive.

There is a thread somewhere where I posted the Shot Gun Cleaning Brush sizes. I am sure a stainless Steel Shot Gun cleaning brush would work fine.

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84 300D, 82 Volvo 244Gl Diesel