Here's an interesting (for you, painful for me!) failure mode. I recently had to have the head pulled off my 1998 E300 turbodiesel to remove a failed glow plug which simply would not release its grip on said cylinder head. That sucker was really in there!

Turns out the root cause of the problem is a failed glow plug relay. It ran the little suckers too long, causing them to warp, and mechanically locking them in place. Ouch.

BTW, three separate machine shops refused to work on the OM606 head. Because the glow plugs are almost six inches long, they had no confidence they could remove the plug without destroying the head. I was _this_ close to buying an new head casting for $2300. Fortunately my mechanic is quite a diligent fellow and took it as a personal challenge to remove the recalcitrant glow plug. It required two weeks of patient work, but he did it.

All this headache caused by the failure of a $100 glow plug relay.

I don't have the car back yet, but that ought to happen tomorrow or Friday, whenever the new relay comes in. All that's left is to wrangle with the extended warranty company about what they'll pay. Glow plugs are not covered, but the relay is. But what about collateral damage caused by a failed part - namely the relay?

- Jim

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