Hey guys, well I started what I thought was a simple thing, only to find out I had the wrong part. I had ordered the factory om 603 block heater to replace the burnt out one in my 300d (burnt out last year when I had my head issues and air pockets in the cooling system), but didn't realize I need an adapter, etc. I unscrewed it with a large socket, and although it required a bit of force came out uneventfully. I went to put the new one in, but alas it is smaller and the threads don't match!

Anyhow, long story short...I ordered another one with the appropriate adapter but it won't be here until next week. I would like to make the car driveable again in the meantime. The seal on the original one fell apart when I unscrewed it, so I am wondering if I could use some type of rtv or thread sealant to seal the old one back in? What do you guys think? If it seems like a bad idea I guess I can wait a week...I just feel bad for borrowing my neighbors car all week (although it is a nice almost-new Cadillac STS)

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97 S500 (90,000 miles) - wife's car
87 300D (298,000 miles and a replacement #14 head)
94 Suburban K2500 - need something to haul firewood
83 300SD (343,000 miles) (sold)

Not speaking from experience of the block heater, but....Should be an easy sealing application for RTV, ~15 psi of the cooling system, your pipes at home have 50-60psi. Pipe dope would probably work if you didn't want to remove it easily...

That said, drive the STS, it will make you appreciate a new car and the 124 at the same time!

Have been wondering about the adapter myself for the CDI, seems like almost any MB Diesel (240D, etc) block heater would work... What is the adapter PN?

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05 E320 CDI
99 SL500
02 530i

82 240D SOLD
83 240D Euro 4spd SOLD
86 300D Euro Auto SOLD

Good call on the rtv...I will probably do that for now just to get it back on the road...I do want to be able to take it back out easily. I only wanted to ask and confirm b/c I am so paranoid about this cooling system after what I went through a year ago!

The STS is really nice to drive. I will say though, I am very impressed with the fit and finish of a w124 compared to a newer car.

On the note of the adapter, I came up with dead end after dead end with Mercedes. I searched forums, went to the local MB parts counter, and looked on a bunch of websites. I heard from multiple sources that Mercedes stopped manufacturing that adapter about 10 years ago because it was considered an "accessory." I ended up calling auto****az, and they sent me an aftermarket block heater made by Zerostart that includes the adapter for $70. If I were to do it all over again, I probably would have just listened to the advice on other threads and put in a lower radiator hose heater. Oh well!

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97 S500 (90,000 miles) - wife's car
87 300D (298,000 miles and a replacement #14 head)
94 Suburban K2500 - need something to haul firewood
83 300SD (343,000 miles) (sold)

Block Heater - Wrong one? HELP! - Mercedes-Benz Forum

....Oh yea, seems to go in circles on the adapter. Sounds like you have a solution at least.

eBay shows some variety as well. Still not clear to me if the CDI would need an adapter (from my reading), probably best to grab one.

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05 E320 CDI
99 SL500
02 530i

82 240D SOLD
83 240D Euro 4spd SOLD
86 300D Euro Auto SOLD