Good advice on the thread, I always put some anti Seeze, its important as they don't get stuck.
The build in carbon would burn with the heat created by the glow?
The build in carbon related to my letter is because they were "DEAD" or "BURNED". Of course the carbon will build up, there is nothing to burn it as the glow is not working.
also after those NGK, when I put the new BERU in, it was tighter abd I had to push them in, this with the carbon build up, then there is a problem with the NGK been slightly too thin compare to the BERU, making them building up carbon in the HOLE.
Again, NGK is a No NO go

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E300TD year 2000. RUSTY SOLD
cost a fortune to maintain on the road
but run well on WVO
Second Merc died due to corrosion ( NOT rust) How can mercedes get away with that for so long?
Third lasted a month then went away...
Fourth now... Corroded too...