Ordered a block heater from www.autoanything.com. When it came I successfully removed the old plug from the block, but the new one I got would not thread in, it was too small. It doesn't seem to be after-market, the box it came in said Mercedes-Benz of America, etc. Don't know if it's just a parts mixup or if anyone else has had this problem. Put the micrometer in the hole and it said 37 mm without the thread. The thread on the plug I got from autoanything seems to be standard, and the block seems to be metric. Has anyone else come across this? Has anyone successfully purchased one online from some other parts store? Any help would be appreciated.

Try posting the question in the diesel section.

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1976 240D
1976 240D parts car
1970 220D daily driver

The only quick fix I can think of is to take the plug you removed and the heater to a large hardware store and see if they have a reducer you can use to fit the two together. You just need a reducer that has your 37mm metric threads on the outside and whatever the heater threads are on the inside.

You might wind up going to several places before you find something that fits, but this would solve your problem.

there is an adapter to make it fit. If you order the block heater from a mb parts place it usually comes with it, although you may be able to order the adapter separately.