I was changing the water pump and drained the radiator, via plug on the bottom side, on my 2014 E350 Wagon.

While trying to drain faster, I thought the piug has to be turned out.. and maybe I was wrong there?

Internet suggested it is simply a petcock, you turn 90 degrees.

Now that I tried to close out, it can be rotated, over and over again, it does not look, and it does not come out.
Internet suggests it is only held by the seal- friction now? That tabs may have broken.

Has any body had this occur, or knows if simply leaving the drain plug in horizontal position will seal safely?

I am concerned to warm up the car, and have it lunched out by the cooling system pressure.

Thank you.

I bought new drain plug for $9 from MBZ local dealer, will insert it now.
https://www.fcpeuro.com/products/mer...xoCvhoQAvD_BwE


Only mystery is how to insert:I believe in OPEN position, while the tabs lock in COSED position.

I'll pull with pliers in OPEN position to see if it slides out easily.

Worked, installation is a little unusual, it's at an angle a bit, you push gently with greased seal, and rotate until it suddenly kind of slides in and as you turn it locks/stops.
That is it. It's locked in pretty much near Vertical Line/Knob direction, a bit off center.

It has two 90 degrees rotation steps. When opening you first turn 90 degrees CCW, pull it out about 1/2” , then turn another 90 degrees and after that you can pull it all out.

When turning you must not force the turn after the 90 degrees as you would break the tabs.