The 240D has an iron block that probably is pretty safe as far as removing the freeze plug is concerned unless the block already has some problems. I also wouldn't try it on a block that's outside and stone cold in 30 degree weather. Start with a warm engine and you may want to heat the freeze plug a bit more as well. I wouldn't overdo it but I'd give it a go. Let us know how it turns out.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold