glow plug spinning, but won't come out.

[treeroot]

Mercedes diesel engine, glow plug was tight, but it started to loosen up bit by bit. Became easier and easier to unscrew, but now the glow plug spins and spins but isn't coming out.

Is my glow plug broken?

Or is the tip swollen with carbon and holding it in?

[partsman]

Could be carbon built up, any chance you can spray some carb cleaner or something along side it, maybe it will dissolve the carbon.

[amosfella]

what engine?? and is it plug nearest the firewall??

[Kristopher10]

Did the glow plug actually unscrew from the engine or did it stay in the same position and just spin? If the it's the second one, you've probably got no threads left in the engine and will need to do some more disassembly to repair it.

[amosfella]

Common problem with mercedes diesels. I've rarely seen one strip out. Fire it up, and that'll pop the plug right out.