Yes. Exactly.

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Mike Mass
Freehold, NJ

1999 E300 TD 178,000 miles
2007 E320 Bluetec - Sold

1998 E300 TD - R.I.P.

That gaping hole is a lot bigger than I could make out from the photos. I'll draw up a diagram later.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Did you remove the injector and cranked the engine? If you haven't cranked it yet. Put a towel over the head so you can see which holes had water coming out.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

For such a large gaping hole that is 1.25" deep all around in the intake, epoxy putty is not going to work. Below is what I'd propose. The 14-1.5 mm machined bolt's purpose is to apply pressure on the lead plug which pushes on the remnant of the glow plug, trying to do the same thing as when you tighten the glow plug. Whether this will work or not to keep combustion gas from escaping depends on whether the glow plug seat is intact and if sufficient, even pressure can be transferred to the glow plug seat.

The 1/4-20 N.C. set screw pushes on a rubber plug which seals the coolant breach. Coolant pressure is determined by your expansion tank cap, which should be around 17 psi max.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Are you sure putting a rubber plug that close to the combustion chamber is a good idea? I think it might not be.

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Garage:

2017 Chevy Colorado Diesel (nanny state emissions)
2005 Volvo S40 T5 AWD, 77k
1987 Mercedes-Benz 300D turbodiesel, 4 sp auto, 156k - 28.7 mpg
1996 Tracker 4x4, 2 door, 16v, 3 sp auto. 113k - 28.6 mpg

WARNING: this post may contain dangerous free thinking.

If you look at photos Mike posted, the tip of the rubber plug breaches a small hole (approx. 1/16" ? diameter) into a coolant jacket, it sees coolant temps, not combustion temps.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

So what was the outcome of this fiasco?

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now