Early this morning I was greeted by the surprise of finding a large puddle of fluid right in front of my '79 240D: the radiator drain plug all of a sudden leaked and fluid is no longer visible inside the radiator.

Now, isn't this strange? Not a fluid leak during my over three years owning the car and now, out of the blue moon, all that radiator fluid on the garage floor overnight...

So, my question is, is it just a tighter drain plug I need, or should I be concerned about some potential major problem that might have caused the sudden leak?

I tightened the drain plug with a screwdriver - not realizing that the plug is made of cheap plastic - and in the process split it in a half (it still holds the fluid though).

I need to drive the car ASAP and have no time to drain and refill the radiator... What should I put in - suggestions, please? I heard that distilled water mixed with some strongly anti-rust anti-freeze is best. What product do you advise?

Thanks so much,
Rino

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

How do you know it leaked out of the drain plug?
Did you see drips coming from the plug area?
A leak from the water pump or water pump housing would end up in the middle front of the car.

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Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

How long does it take to drain an empty radiator?

Fill it with water and drive. At least half of the original coolant is still in the block.

It's coming from the bloody drain plug... I just checked a few minutes ago, and it is still leaking from there... Tightening it did not resolve the problem. Anybody knows what's going on with this leak? (could a worn out washer in there be the problem?)

It's not empty, and it is still leaking... I'd like to put in half water, half coolant - so I'd still like to know what's best coolant to put in.
Also, what's the best place to quickly get a suitable plug to replace the broken one? Thanks.

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

The plug may have already been split from someone else doing the same as you did - tightening it w/a screwdriver. The required torque is minimal. The manual says to use a washer or coin to tighten. This alone tells you how much torque to apply. For the meantime, you can use plain water and baking soda until you get it filled w/coolant.

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Don't Chrome them; polish them

I guess that, somehow, I got confused.

Is the radiator cracked? The drain plug won't just fall out, something cracked.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

You can buy a new plug - from Fastlane (buy parts link above) - but that sure doesn't help you for the next day or so!

Maybe call a NAPA and see if they have one?

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

Actually, it was MY fault - this morning. I used a phillip screwdriver and it cracked right in front of my eyes. Any idea where I can get a new one - do places that carry radiator caps also carry this type of drain plug (I strongly doubt it...)

What brand/type of coolant should I get??

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Understandably so... sorry. What I meant to say is that early this morning a lot of fluid had come out, and it was still leaking. Then, after tightening it, it apparently stopped. But later, when I went downstairs to check again, it was still leaking, a bit less than before, though.

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Nope, I checked. The dripping is coming out of where the drain plug screws in. That's what I don't understand... how come all of a sudden it started leaking... and why, even after tightening it, it still leaks. I am thinking of getting a new drain plug (and washer?), taking the old one out, putting the new one in... to see if that fixes the problem. Where do I get a new drain plug, though?

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

Closest NAPA is a 20-mile drive away...

Does anyone have any idea what might have caused it to start leaking like that all of a sudden?

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1979 240D, W123, 105K miles, stick, white w/ tan interior.

That how things happen. One day it's fine, the next day it's not.

It's a 30 year old plastic part. It lost it's seal probably because of pressure, heat, and age. Perhaps a road debris incident. Who can say for sure? What kind of an explanation do you seek?

Get over it, find a replacement part and move on.

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Question Authority before it Questions you.

Use Zerex G-05 or MB coolant from the dealer.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I'm still a little leary of the diagnosis you provide...
I.E. Radiator Drain Plug,with no human interference,suddenly begins leaking.

However it's always possible that the "PLASTIC" heat stressed and cracked
after YEARS of use.(We will not address if the engineers in Stuttgart had any
input in the final plug product...or if it's just some "Off the Shelf Crap" from
a Forth World Country gifted upon the Mercedes by a P.O.)

I'd be Ecstatic if damage were not done to the female portion of the Radiator
receiving the plug (Threaded) if it is also "Plastico".

(If they made a micro inch torque wrench I'd have one...My great Big Meathooks
have Over-Torqued and destroyed so much over the years ,I can't count the
damage anymore)

A proper pressure test of the system would be in order , once repairs are made..."Just In Case".

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'84 300SD sold
124.128