Is this the thread you were thinking of?

THE Definitive Block Heater Coolant Plug Removal Thread


This is the Wiki on it.
PeachPartsWiki: Block Heater Removal

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

That's the one. Seems like removing engine should be first step!

BTW, I edited my previous post regarding rad hose heaters:

I sent an email about this to Diesel Giant (who sell hose heaters), but no reply yet.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I can testify from my own experimentation that they are useless because they cannot hear the thermostat up enough to have it open, hence the warm coolant cannot circulate to the block.

If the car is fully warmed up and the thermo is open it will keep the coolant circulating for a few hours at best.

You would have to drill holes in the thermostat I think

I don't think you would want to do that, but that's another discussion!

What you could do perhaps, is put a tee in the lower rad hose above the heater and run a smaller hose over to a nipple installed on the block drain plug hole. Maybe put a valve in the line. That would at least get the hot water into the block. I think there may have been a commercial unit designed to do something like this, but I have not seen it.

By the way aieeegrunt where in Canada are you? Your weather sounds worse than ours!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I ran a lower radiator hose heater (100w?) on my 617 and it helped cold starts considerably. An upper hose heater wouldn't do much, but lower definitely does.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

THE Definitive Block Heater Coolant Plug Removal Thread
I strongly suggest you read the full thread.
This plug is a major PIA to remove.

Here are suggestions for other options.
Engine BLOCK Heater ideas

I hope you will read through this thread also.
Cold weather starting links

.

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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

How about using a Wisconsin block heater?

Attached Thumbnails

 

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2012 B Class

1981 300D - Now with greazzer

Ya there could certainly be other unintended consequences from drilling holes in the thermostat to be sure, although I have heard of people making a "summer thermostat" by drilling holes.

The other option is heating up the thermostat housing somehow. It's aluminum isn't it on a 1978? So sticking a magnet heater to it wouldn't work. Probably a bad idea anyways.

What about the hoses that supply heat to the cabin? Or are those behind the thermostat as well.

Just outside Owen Sound. The whole region has been shut down for most of the week. We've managed to somehow combine extremely low temps with massive snowfall, which I thought was physically impossible, but nature finds a way.

I live in the country and don't have a garage, so the car is exposed to tundra winds.

A lower radiator hose should work in the W123. It is just much less efficient than a block heater thus has to be much higher wattage than the block heater since it has to heat the coolant in the hose up first, wait for the hot coolant to rise up to the thermostat to open before warm coolant can begin to circulate in the block. W123 block heater is 400W. I think lower rad hose heaters start at 1000W and go as high as 1500W. At the kind of power, you have to be real careful with the install so it does not start a fire. That means do not wrap the heater with any kind of insulation and make sure it is not near anything that is flamable that can catch on fire.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Got the Bosch 49-850B at PepBoys, out the door for $98.36. 20% off online order minus another $15 core charge. 36 mos free replacement, etc.
Still need to get my lower rad heater installed. Should've had my shop do it last week when I had the valves adjusted and my oil leaks fixed.
I still need a decent starter and winter oil. I diluted the Rotella 15w40 with Marvel Mystery Oil and it seems to thin it out. Still getting a long, hard start below zero, afraid it's going to kill the starter. Tooo cold to check glows, but they were changed in '09, prolly a couple are dead.
This is the '84 300d I had shipped to me in Cincinnati from Portland, OR back in sept.

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'82 240D automatic to manual (sold)
'84 300D (sold)
'12 MINI CooperS Coupe
'71 Triumph Stag
'76 MGB
'08 BMW 535XI wagon
'12 VW Golf TDI

Seeing you have nothing to lose, you could try heating the thermostat housing witha hot air gun and see if that will open thermostat. Then your rad hose heater might keep the circulation going, but unless you get the bypass to close @ about 94C, you may just be heating the rad But maybe worth a try.


I think I have read some posts about tying into the heater hoses. Have not studied them. I am sure there is something you could do to get the hose heater to be effective but may be a summer job (By then we forget about these things!).

We had Tundra swans here this fall - but even they have gone South

I don't think my car would start either if it was left outdoors. When I worked, just leaving car at outdoor parking all day was enough to require a tow when temperature were really low. One other guy had an SDL daily driver - he some how got them to run an extension out to the parking area for him.

BTW, have you checked to see if there is a block heater installed? I know that is not easy to do at this time of year.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

My block heater stopped working, which is why I installed the hose one. Perhaps there should be some sort of forum announcement about this, because it was searching the forums for alternatives that gave me the idea to install this thing in the first place.

I am assuming that the thermostat is working properly; if it was stuck shut I'd have overheating issues during normal driving.

I suppose I could install another one between the thermostat and the block. That would be fun in this weather. Heat rises, I wonder which heater would "win" and which way the coolant would flow.

Gett yourself one of these:

RadioShack True-RMS Digital Clamp-on Multimeter : Multimeters | RadioShack.com

Make sure all lights and accessories are off. Turn glows on while some one watch the meter (readings will drop as the plugs get hotter). If you have 5 working glow plugs you should get an initial reading of around 100 amps. If you get initial 80 amps, one glow is out, 60 2 are out etc.

Here is mine (92.8 amps) clamped around the battery ground cable approx 3 seconds after glow started, which tells me all 5 glow plugs are drawing the correct amount of current and none are burned out.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Many report not working block heaters due to missing cord or possibly a bad cord. I'd suggest checking the heater at the connector with an ohmmeter first. Chances are it is still good (a good heater should be 36 ohms for a 400W heater). From what I've read, replacement cords are hard to find. A way around that is get a cord from an old cloths iron or toaster and crimp on terminals that fit the block heater and glue it in with RTV. Strain relief it so it doesn't get yanked off.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

This is the block heater plug on my 85. It was under the bumper with the cover on when I found it. I don't think the PO ever used it or knew of it's existence since it was always garaged and they didn't drive it much in the winter.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked