kennedymiller

Good Evening guys I have a 2012 ML 350 Bluetec. A couple of days ago I got a check coolant level light come on my car. I went out and looked and it was fine, more than enough coolant. It went away and then it has periodically come on and off since then I was wondering if anyone had any insight into this. Thanks.

Etienne Lau

How are you "checking" the coolant level? On page 367 or there about in the owners manual. There are instructions on how to do this properly:

1. Let engine cool down.
2. Open Coolant cap slowly on the reservoir.
3. Look at the level of the coolant in relation to the Marker Bar.
4. If coolant warm it should be about 1.5cm/0.6 in above the marker bar.
5. If coolant cold it should be at the height of the marker bar.

My 2014 ML 350 Bluetec, during this past winter, the coolant level light would come on when it was cold and go away after it warmed up from driving around on a regular basis. I followed the above steps and found that indeed I was down below the marker bar when it was cold. Bought me a jug of pink Zerex coolant and poured some in to bring it to the warm above the marker bar and problem has not come back.

chassis

If the vehicle is indeed full with coolant, following the procedure above, I would suspect a failed or dirty level sensor. The sensor should be found attached to the reservoir tank, as in my other M-B vehicles. It may take disassembly of other parts, before reaching the coolant level sensor.

There are many threads on this. The coolant sensor appears to be inexpensive, and the replacement seems not too difficult. Need to do some digging to find the right sensor part number for your vehicle.

jfk-usaf

This happens to my 14 as well. Its been talked about on this site. Check your windshield wiper fluid level. Mine ran low and the low coolant indicator came on. My coolant level was fine so I just filled my wiper fluid up and the alert disappeared. Its weird I know but it happened twice over this last winter and the same solution worked each time. They must share a circuit / system or something.

Etienne Lau

There are actually 2 different lights on the dash indicating each fluid. One for windshield washer fluid and another one for coolant level. Is it possible you got the symbols confused? See below as copied from the Owner's Manual.....So I doubt that they "share a circuit/system" as you suggest.

jfk-usaf

Nope. It actually spelled out coolant in the message.

Koenig1

I had the same message on my 2015.... The coolant level sensor is finicky. The problem usually arises as the outside temperature cools down overnight, as in the Fall going onto Winter. Best way to get rid of the headache is to add 1/4 cup of Distilled water to the system. It really doesn't take much to make the irritant go away.... that is if your coolant system is definitively full.

Etienne Lau

Something strange there. I got separate indicator for both coolant level and windshield washer level. And the bottles are in separate areas on the vehicle. I know during the winter, the coolant light would come on while cold and go away once the coolant warmed up and the level came back up. So am I scratching my head understanding how you got ONE indicator for coolant and Washer, and fixed it by filling the windshield wash bottle.........since there are 2 separate circuits and 2 separate dash indicators.

Etienne Lau

Definitely no sharing of circuit or system as you suggest. I just ran low on wiper fluid and coolant level is fine:

Barry45RPM

The sending unit is VERY sensitive and even though it looks full enough for you it doesn't satisfy the sending unit. Been there, done that.