Radiator drain plug SUDDENLY leaked!!! All fluid on garage floor.
 

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

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.

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.

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.

I guess that, somehow, I got confused.

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

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?

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??

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.

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?

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?

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.

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

Prognosticating
 

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".