I have a w222 2015 S class Diesel, I have a serious coolant leak, having checked all the usual places I can't find the leak. I have used a boroscope and Identified pooling coolant around what appears to be a sensor inserted vertically into the sump on a horizontal ledge of the sump on the left front corner of the engine. I don't know what this sensor is, not sure if there is an oil cooler in the sump. Mercedes are there usual unhelpful selves, I don't want to remove the sensor as its a big job until I know what it is and if its connected to the cooling system. There doesn't appear to be any leakage from above but, again this is through the eye of a boroscope. Anybody have any idea what this sensor is, I am based in Ireland so its a right hand drive version. Appreciate any assistance.