Broken Glow Plug - Searching forum didn't help!

[fstmatt]

I promise everyone I searched first for a solution, and I think this is a "different" broken glow plug problem.

I troubleshooted the GP system per instrucions on Diesel Giant's site, and found problem with plug #1. Removed the plug, and the heating element was... missing. Replaced the GP, car ran great for ~< 1 hr. But then GP relay light stopped lighting again. Pulled plug 1, and same thing - the heating element was been cracked off!

Any ideas of what can be cracking the glow plug? Since the GP is stationary, it can't be clearance b/w the piston(?). Could a stuck or badly misadjusted valve push down that far? What else is rattling around and destroying the glow plug?

I fear my engine toast - but hopefully someone can give me some good news...

'81 240D 616 engine.