I can start my engine that has 300K+miles with 325-350psi compression outside in -10*f weather using only the glowplugs. If I were you I wouldn't worry about a block heater unless you expect to drive in sub-zero weather. Even in that case, its much easier to install a hose heater than mess with the block plug.

Are you sure you don't have a heater that is just missing the cord?

get ready for the ride of your life if you want to put one in. I would just hand my car over to a mechanic and let him have some fun for a day.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

It was 95F here yesterday ---- how can you think about a block heater?

If you really think you need a block heater, then have you considered finding a car that already has one installed? Sounds like that might be easier.

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Ted,
No offense to you, but if you can't locate a 19mm wrench, you're the wrong guy to start this task. Return the block heater, and buy a heater that splices into your heater hose. It's a 1/2 job as someone else stated, and they work great. The chances of something breaking or otherwise going wrong is higher trying to remove that heater core plug. I've owned over 500 cars and can rebuild transmissions and engines, but decided not to mess with the block plug. Why make extra work for yourself.

If you have the manifolds off it will be easy. I did mine this way. Go to one of those surplus buy bolts by the pound places. They will most likely have a bin of tooling stuff. I bought my 19mm allen wrench for 2 bucks! Then I used a big pipe wrench (the one that one has in the corner of the garage for this very job) this thing is about 4 foot long!
Using the pipe wrench does not limit you like the big piece of pipe does on an allen, and you can get the wrench close to the plug for better power.
Good luck,
Tracy

Heating the block around the plug with a propane torch is also said to help the removal process. In my case ('85 300D-T CA w/trap cat) I couldn't even see the plug. My mechanic recommended against trying to remove it -- he said it would take several hours and something would probably break in the process, given the age of the car. Accordingly, I installed a lower radiator heater using the kit that Diesel Giant sells. It heats the water jacket to about 60C in 4 hours.

Even during the trap cat removal process (for testing purposes only ), with everything off but the manifolds, I couldn't see the plug. The only one I could see was the block drain plug. If it was the case of "no other way," I could understand but it's so easy and inexpensive to install a radiator hose heater that there's just no justification except in the case of a show car where everything has to be original.

The W123 cars had the factory block heater as a free option during the first year of ownership. You asked the dealer and he put it in. Most warm climate owners never bothered. It's also possible that cold climate Benzes had heaters installed at the factory -- I don't know.

Later diesels (OM603, etc.) had the block heater installed at the factory and you just had to ask for the cord. Again, most warm climate owners never bothered. Even my '87 300D Turbo, originally from New York, did not have the cord.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I removed a number of block plugs to install the heater. I used a 3/4" drive T-handle and socket along with a 6 foot pipe-and a pencil clamped between my teeth. This was 20 years ago. I wouldn't attempt it now for fear of breaking the block, as others have posted.

http://www.pts-tools.com/

KP3035279 1 Snap-On/Williams - 19mm Hex Bit Socket Standard Length 1/2 Drive
Price: $14.40

Part Number: KN5310988
Description: Bondhus Ball End Hex Key -- 19mm Long Arm 11-1/4'' Arm Length
Brand: Bondhus
MFG Part #: 10988
Availabilty: 8
Price: $24.35
http://www.pts-tools.com/


http://www.mcmaster.com/#metric-allen-wrenches
Metric Sizes
19 mm 10 13/16" 5503A56 $19.64
http://www.mcmaster.com/#metric-allen-wrenches

i have installed block heaters probably about 10 times. i always buy what i consider to be the proper tools.snap on for best precision craftsman for 1/2" drive. my 19mm allen is 1/2" drive snapon and the socket {forget size} is craftsman.i must not have installed one on a 300sd in the car because i do not remember removing manifolds.i only remember removing starter when in car.when doing an engine swap i always put in block heater. a local shop i know uses a lift and a 6' cheater bar. i have never had a lift but i love cheater bars.