I removed an old glow plug, which I suspect as weak, from my 85 300SD. The old one came out uneventfully. On trying to install a new one I just can't seem to get the threads to engage. I looked in the hole as best I can with an inspection mirror and I can't see any bunged up threads. The threads on the old plug show no signs of damage. The threads of the new plug look good. Any hints as to how to go about getting this thing in?

Yes. I am turning it clockwise and it is square in the hole.

What is the best way to chase the threads without pushing debris into the combustion chamber?

I aplogize for the silly sounding question, but I fooled with this *&##%$ thing for an entire hour last night without success!

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1985 300SD, 203,000 miles, dark blue

Lil Sarah says: "Poor old Grandma Blue Car...She's sad."