One of our customers called us recently to ask if we could help them out with a problem Mercedes. They had a C-class in their workshop to have the glow plugs replaced and what they thought would be a simple job had turned into a bit of a nightmare for them.
Three of the glow plugs had been removed without any problems but when the fourth one was removed only part of the glow plug came out. The picture above shows that the outer casing of the glow plug had unscrewed leaving the glow plug element and electrode stuck in the cylinder head. The garage owner had tried to pull the remaining part using vice grips but as there wasn't much room he couldn't get a good enough grip to remove it.
Although it is not common for glow plugs to break like this we do have some specialist equipment which can remove the element and electrode when they are broken like this. The special tool clamps tightly around the glow plug electrode and by using a sliding hammer it is often possible to remove the element and electrode in one piece.
We managed to remove the remaining part of the glow plug on this vehicle, saving the cost of having to remove the cylinder head.