Thanks but I can't watch in till I get to the Library Computer my dial up is not up to it.

I know that bronze Gun Bore Brushes come in different sizes.

SHOTGUN BRUSH SIZES; threaded end 5/16x24 inches in the USA.
Diameter of the Brushes.
10 gauge 0.775"
12 gauge 0.729"
16 gauge 0.662"
20 gauge 0.615"
28 gauge 0.550"
410 bore 0.410"

But some people were scared a bristle might break off and get into the Engine. Even though Diesel Injector Tube Brushes are the norm on Trucks and I have never seen them cause an issue.

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84 300D, 82 Volvo 244Gl Diesel

I wonder if it might be safer to rotate the brush using a battery operated drill rather than pushing it in and out of the hole?

OK I viewed the vid. Looks like a shotgun bore brush and an cleaning rod to me. For some reason the sound was not loud.
OK he said it was for a 50 cal BMG which is like the 50 cal used in the Machine gun.


But, his rig is not going to get into the hole that a Glow Plug Reamer takes care of as it 7mm and the 50 Cal brush is going to be 12+mm.

But, Carbon is not supposed to get beyond where the vid shows cleaning. You should only need to clean that if carbon has caked inside of there.

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84 300D, 82 Volvo 244Gl Diesel

You are correct, carbon should not build up beyond the sealing surface of the glow plug, I just wanted you to see what tool could be used if carbon was to seep up the glow plug.
I will follow Jake12's advice on glow plug replacement, this guy has removed seized glow plugs three times now with success and he explains his method in detail including reaming the glow plug holes.
We can discuss our ideas and methods for this all day long but I will put my money on the guy with the experience every time. jake has been there, done that, and his method is proven. he also offered to help me with my glow plugs if we lived closer together...how cool is that?