Roggez

I have a 2014 model with 42000km on the clock and over the last few months, the coolant has been leaking. I was twigged by the warning in the speedo on start, and I just topped it up and all was well. Unfortunately, the problem persisted and although there were no obvious signs of leaks under the car, I was losing about one litre per 500km. A check around the net for similar problems found nothing so as it was out of warranty, my local garage (an old experienced friend) had a look. To cut a long story short, the O ring on the plastic coolant inlet fitting to the block had failed and much of the loss was caught by the drip trays or boiled off in contact with the block. We had previously pressure tested the system and there were no cracks in the fitting either.
The interesting aspect is that Mercedes has changed the design of the plastic inlet fitting for some reason. The current item(as you can see below) has a two bolt attachment to the block (even though the block has three bolt holes) to a beefed up three bolt attachment and the flange has been strengthened. I can but assume the latter change is to permit the use of a better O ring.
I have been using MBZ specified coolant and was quite astounded when my friend found the cause, which in effect, was a two bit O ring on an expensive car, for which Mercedes customers buyers would expect a better performance. I chose to fit the updated inlet fitting also so the fix was not much change out of $900 of which much was for labour.
Now a happy (but poorer) camper again!