Stuck Plugs in CLK

[Taff107]

Well having had the 40k mile W208 CLK 320 for 6 months the A service light came on and it was booked in for the service. I got a call from the garage stating that despite having a full history, the plugs have never been changed since new and did I want them changed. I gave the go-ahead and they have just contacted me and said that they were unable to do as they were seized tight and didnt want to risk them snapping off. They have doused it with penetrating fluid and said that they will have another go when the engine is hot. Obviously, this isn't good and can do without the cost of head removal and drilling. Anyone have any ideas or what the solution is in this situation?

[P.Nott]

I had a similar issue on a W210 E Class I once owned and the garage did exactly as yours are suggesting. They soaked the plug cavities in penetrating oil overnight, then cleaned and dried the area before starting the engine and getting it very, very hot before trying again. This time they came out with a bit of effort, but at least they managed it without damaging the head.

The theory is that it has an aluminium head which should expand more than a steel plug body, thus making them slightly less tight and therefore easier to remove.

Coincidentally, it appeared my plugs had never been changed either, despite a FSH. Let us know how it goes.