I've managed to replace three of the four glowplugs in my 306 Turbo Diesel (the two at either ends were bastards; lack of access...). During previous ownership one of the glowplugs has been rounded off.
Does anyone have any suggestions on how to get it out? I thought about locking a couple of 8mm nuts onto the electrode and seeing if that would turn it, but a vice test on an old glowplug showed it was dead easy to shear the electrode off. I also considered hammering an undersized socket on and seeing if that would work but the electrode won't allow a standard-sized socket to fit on with the ratchet or extension bar. I guess I could buy a deep socket.
There isn't enough access to e.g. get a pipe wrench or mole grips on.
Any suggestions on how to remove it? I'm obviously conscious that maybe the thing is in there dead tight which caused whoever in the past to round it off, so I'm a little concerned about shearing the thing off which would be a nightmare...