Coolant warning

Page may contain affiliate links. Please see terms for details.

Paradroid

Member
Joined
May 13, 2021
Messages
56
Location
Chorley, Lancs
Car
2020 C300 Coupe (W205)
Hey all. I've got a Jan 2020 C300 Coupe, and tonight I got a yellow coolant warning on the digital dash. Let the car cool and took the cap off the expansion tank. There's definitely coolant in there, but I'm not sure I'm reading the level right. The lower part of the tank is white, the top is black. In the lower part is two raised lines that form a T-shape. I think that is the level guide? It's above that, but it might not be 1.5 cm above when warm so maybe it just needs a small topup.

It does seem like there is a smell coolant when the engine bay is warm, unless it's just warm new plastics. It's a newish car, but it has done 7k miles so it's not exactly brand new. Can't see any sign of leaks though, it all looks fine.
 
Welcome. Take a photo of the message on the dash, and take the car right back to the dealer....
 
BTW, this is how you check the coolant level:

20210527-212110.jpg


With a cold engine, the level should be up to the mark on the plastic strip inside the expansion bottle.
 
Welcome. Take a photo of the message on the dash, and take the car right back to the dealer....
Yeah that's one option. I just wondered if it might need a small topup. Does seem unusual though for a new car doesn't it.

Something else odd - and bear in mind the car is new to me, so this might be normal, but with the heater set to LO (and the air con off), the air through the vents feels a bit warmer than the outside air. It's a bit of a stuffy cabin.

Temperature on the dash is reading 90 degrees though, perfectly normal.
 
Thanks @markjay appreciate the photo. My c205 tank looks slightly different. The manual wasn't very clear first time I read it but I get it now, it is the T-shape. It's currently sitting above the T (which is expected for a warm engine). I guess the answer is to wait for it to fully cool, then see if it's still above the marker.
 

Attachments

  • c300-coolant.jpg
    c300-coolant.jpg
    84.4 KB · Views: 14
Going to take your advice Mark, and call the dealers in the morning. The warning combined with the air vents and the possible coolant smell makes me think it needs checking, I'm hoping they can at least do a quick once-over without me having to book it and leave it in for ages. Really wanted to get some miles on it this weekend, not sure I can now without getting it checked over.
 
Called the dealers - nothing for a week without a courtesy car or 3 weeks with a courtesy car. Bit disappointed that they can't prioritise a quick check over the car to establish if it's ok to drive - take it that's normal, they're probably stacked with recall work if it's anything like the BMW garage I used to deal with before getting this car.
 
Para , seems a bit odd that a car with just 7K on it needs a top up , but once topped up you can keep an eye on it .

Regarding your 'Air con' if it is on LO it should be blasting cold air like mad , noisy enough to make you turn it up in a short time just to give your ears a rest. Your climate control should be on at all times on this car just set it on AUTO and move the temperature control as and when you need to.

Best to use the full climate control function rather than just 'air con' .
 
Cheers Pete. I should have mentioned on my message above, went out again this morning to check the car fully cold and the level is definitely fine, it doesn't even need topping up. It's something else, either a faulty sensor or an issue somewhere else in the cooling system. Didn't expect to need an ODB2 scanner with a year old Mercedes but am considering ordering one :D
 
In essence, if you are concerned that perhaps the car shouldn't be driven, you can always call-out Mobilo roadside assistance, and they'll be able to advise. That said, I don't think that in this case there's a cause to be concerned about driving the car.
 
That's exactly what I ended up doing!!

The recovery guy has just left now. He thinks the car is ok to drive and whatever it was is electrical, not mechanical. Running temperature is 90 degrees as expected. He said there was a stored fault code, but it wasn't low coolant level - it was something about coolant pump pressure. To me that's either a glitch or the start of a water pump failure. Water pump is electric on m264 engine.

Planning a long drive Sunday but will take a few shorter ones and see how it holds up first. Still booked in dealers next Friday.
 
Cheers Pete. I should have mentioned on my message above, went out again this morning to check the car fully cold and the level is definitely fine, it doesn't even need topping up. It's something else, either a faulty sensor or an issue somewhere else in the cooling system. Didn't expect to need an ODB2 scanner with a year old Mercedes but am considering ordering one :D
I have always advocated on here anyone with an MB 'of a certain vintage' should own a decent OBD scanner. In my mind the vintage would be about 2010 , I would hope owners of one year old cars would not need the use of one ! :D
 
Hopefully the final update on this one, I didn't get any more issues in a few hundred miles of driving, and car has now been checked over at the dealers and they found no fault either. They say they topped up the coolant slightly so it will be interesting to see what level they think it should be at.
 

Users who are viewing this thread

Back
Top Bottom