I just leased a 2020 C300 4Matic Sedan with AMG, Premium, and Multimedia packages. It is a fantastic car; however, when I first drove off the lot (it has 37 miles, because it was driven to the dealership I was at from another) an immediate yellow coolant warning light came on. As I was driving I noticed the temperature of the vehicle had not changed. I pulled over, called the dealership and they said come right on back. After I turned the car back on it was not there, I drove for back and it turned back on. The dealership took it in and topped the coolant off, and then drove around and said it didn't come back on. I then drove home and the light did not display again. I have since driven the vehicle for short trips where the vehicle is allowed to come to operating temperature, and some days the light comes on and disappears, other times it keeps throwing the warning until the car is turned off. It has never increased the temperature so the system is cooling the vehicle and heating it up from a cold start. Any thoughts on this phenomenon? There is no leak from what I can tell, and the only thing I can think of is that it is a faulty sensor. However, it has to be a replicate-able issue with the vehicle before Mercedes will change it under warranty, and everyone knows once you have a problem and you go to the dealership it suddenly disappears.

 

For issues like this after the issue comes up and disappears, Send it in and allow them to have it a few days. But keep in mind it isn’t a big issue, temps haven’t changed so it isn’t a big deal, I just filled mine with water every year, about 500ml. No leaks. Since you already reported it if something happens they’ll cover it don’t worry.

 

Appreciate your quick response. I was going to tab this under the usual german car adage, if a light turns on and off it's not a problem until it turns red. It's also a new car so I'm letting the engine settle a couple thousand miles, before reporting anything immediate. I'll continue to monitor. Thanks again

 

it's not though. If it's full and still showing this message, its a bad sensor. Take a picture next time.

 

There's not enough info to make that diagnosis.

OP, take it in and leave it with them until they fix it. Demand a loaner and drive it like you stole it until you get your car back.

 

Letting it ride is a really bad idea. That said, it's your car and your money.

 

Take a picture or video next time (or times).

 

I will take a video of it next time it happens, and will report back. I will also take in the vehicle next time it happens, and make sure to leave it with them longer.

 

With the car cold look in the coolant tank and see if the level is below the sensor. If the coolant is over the sensor then it's a bad sensor. When the car is hot of course the coolant expands and should cover the sensor. It could be some air trapped in the system but by now I would think it would have been cleared. Pictures with your phone are great for little Gremlins line this.