Coolant level warning light issue

[Rob Garner]

Hi all,
Have an Ml 2003, best car I have ever owned, however, just recently the coolant level light came on, worried about it going into limp mode, especially on a long journey, decided to attempt a remedy and bought a dealership genuine part header tank and sensor (new), and fitted it, coolant level good, no leaks, no overheating, but a few days later the light came on again. Any clues?

 

[Linuus]

Make sure you use the right coolant and MB one and mix it 50/50
From what they told me at MB adding just coolant may not help on conducting the heath from the car all over to the radiator, and there for wrong reading from the thermostat.
Are u using red MB ou blue coolant?


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[Rob Garner]

Make sure you use the right coolant and MB one and mix it 50/50
From what they told me at MB adding just coolant may not help on conducting the heath from the car all over to the radiator, and there for wrong reading from the thermostat.
Are u using red MB ou blue coolant?


Sent from my iPhone using Tapatalk

Hi, Thanks for the reply, bought Mercedes recommended coolant.Blue.

 

[Linuus]

Hi, Thanks for the reply, bought Mercedes recommended coolant.Blue.

Did u mixed 50% water 50% coolant?!


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[ajlsl600]

get a cheap cooling system pressure test kit , like at machine mart ,or borrow ,pump up to cap pressure, observe visable leaks. if press continues to drop and no leaks seem anywhere.check WELL .. loose the sump plug a few turns, no need to take out ,look see if any water
.https://www.machinemart.co.uk/p/clarke-cht694-radiator-pressure-test-kit/

 

[Martin Jennings]

It may not be connected to your problem but my C Class had the coolant warning coming on despite adequate coolant being present. I also had a warning for low screen wash fluid and it turns out these 2 sensors are wired in series giving false readings for coolant when it was in fact the screen wash level sensor that was faulty.

 

[ajlsl600]

It may not be connected to your problem but my C Class had the coolant warning coming on despite adequate coolant being present. I also had a warning for low screen wash fluid and it turns out these 2 sensors are wired in series giving false readings for coolant when it was in fact the screen wash level sensor that was faulty.

sounds a daft idea.

 

[Martin Jennings]

sounds a daft idea.

I agree! But thats what it was.

 

[Taffy7hfa]

Mine had a small leak from one of the pipes near the bottom of the header tank which is very common, maybe fitting the new tank hasn't fixed the leak ? Is your car leaving a little "wet patch" for you after being parked up ?. Getting all the air out of the cooling system on these can be difficult, it might have just "burped out" an air lock which would cause the coolant level to drop.
Mines an 02 facelift which I've had for about 5 years, as you said in your op it's been the best car I have had as well, although I think of mine as more of a truck on steroids....

 

[Rob Garner]

Mine had a small leak from one of the pipes near the bottom of the header tank which is very common, maybe fitting the new tank hasn't fixed the leak ? Is your car leaving a little "wet patch" for you after being parked up ?. Getting all the air out of the cooling system on these can be difficult, it might have just "burped out" an air lock which would cause the coolant level to drop.
Mines an 02 facelift which I've had for about 5 years, as you said in your op it's been the best car I have had as well, although I think of mine as more of a truck on steroids....

No, no leaks whatsoever, coolant level spot on. Got to be related to an electrical fault somewhere, just wondered if anyone has had similarly.

 

[Uncle Benz]

Is the electric radiator fan working? The coolant warning light will come on if the fan fas a fault. On the ML you have there is a strange fuse for the fan sandwiched on the battery positive terminal. The fan units themselves can also fail.

 

[Steve@Avantgarde]

Wiring issue to the sensor? Have you checked the wiring plug pins for contact, voltage and signal?