LOW COOLANT LIGHT WON'T GO OFF

[Noddy 99]

Hello, chaps - hope you're all well!

Low coolant tell-tale came up on the dash so I topped it up. However, the tell-tale is still on...

Possibilities as I see it:

Faulty sensor. I ran an iCarSoft scan and no relevant code was thrown.

System needs pressurising. I've been told that this will self-regulate within a few days - is that correct?

As always, massively grateful for any pointers you can give me!

2009
S211
E280 CDI Sport

 

[Dean Fletcher]

Hello, chaps - hope you're all well!

Low coolant tell-tale came up on the dash so I topped it up. However, the tell-tale is still on...

Possibilities as I see it:

Faulty sensor. I ran an iCarSoft scan and no relevant code was thrown.

System needs pressurising. I've been told that this will self-regulate within a few days - is that correct?

As always, massively grateful for any pointers you can give me!

2009
S211
E280 CDI Sport

So is the coolant going down after topping up?

 

[grahamcol]

This might not apply to your model but l seem to recall the rad level light being related to the washer fluid level. Crazy l know but l think this was the case on the 202. Might be worth checking the washer just in case.

 

[Wighty]

Did you top it up far enough ? There is a small tower marker inside that the level needs to be up to

 

[Uncle Benz]

Is your electric cooling fan working correctly? Put the AC on, see if it runs the fan. The coolant light can also illuminate if there’s an issue with the electric cooling fan

 

[Noddy 99]

So is the coolant going down after topping up?

Only topped it up today so don't know yet...

 

[Noddy 99]

Is your electric cooling fan working correctly? Put the AC on, see if it runs the fan. The coolant light can also illuminate if there’s an issue with the electric cooling fan

I have my AC on permanently and it was working fine earlier...

 

[Noddy 99]

Did you top it up far enough ? There is a small tower marker inside that the level needs to be up to

I'm ashamed to say that I let the guy from Halfords do it as I didn't want to get my hands dirty, lol...

He tried it just a fraction UNDER the white marker and then just a fraction OVER...

 

[Noddy 99]

This might not apply to your model but l seem to recall the rad level light being related to the washer fluid level. Crazy l know but l think this was the case on the 202. Might be worth checking the washer just in case.

Recently topped up so unlikely...

 

[Noddy 99]

Many thanks to all who've contributed so far...

 

[mioba]

Why did you add coolant.
How much coolant did you add.
Have you bled the system properly.

 

[mioba]

I'm ashamed to say that I let the guy from Halfords do it as I didn't want to get my hands dirty, lol...

He tried it just a fraction UNDER the white marker and then just a fraction OVER...

At least you admitted it )

 

[mattkh]

..... I let the guy from Halfords do it

Check the cap of the coolant bottle in case Halfords guy did not tighten it all the way.

 

[mioba]

Check the cap of the coolant bottle in case Halfords guy did not put it back on.

Corrected

 

[Noddy 99]

Why did you add coolant.
How much coolant did you add.
Have you bled the system properly.

Because I was getting the "low coolant" icon on the dash...
A fraction over the white line... He hardly poured any in so it can't have been very low...

Ah - this might be interesting: do you have to bleed the system just for a quick top-up?

 

[KennyN]

Ah - this might be interesting: do you have to bleed the system just for a quick top-up?

No

Have you checked the level now ?

Where is the sensor located for the coolant ?

Did the MB trained tech at Halfords put it in the correct place ?

K

 

[mioba]

Because I was getting the "low coolant" icon on the dash...
A fraction over the white line... He hardly poured any in so it can't have been very low...

Ah - this might be interesting: do you have to bleed the system just for a quick top-up?

If the coolant level became low - where is it going - investigate.

 

[Noddy 99]

Sorry for the delayed reply, chaps...

* Coolant tank cap IS securely affixed
* Sensor is way low down on the tank; far too low down to have genuinely triggered a low coolant warning
* Temperature is normal and stable. Driving up the Burway in Shropshire (an uphill 1:5 gradient for over a mile) DID send the temperature above 100 degrees briefly but that was a high-stress situation
* I had to top up a small amount this morning so it DOES appear to be losing coolant

Anyway, I could chase this for weeks so it's booked in for a proper diagnostic tomorrow. Fingers crossed and thanks for everyone's help so far...

 

[Noddy 99]

This might not apply to your model but l seem to recall the rad level light being related to the washer fluid level. Crazy l know but l think this was the case on the 202. Might be worth checking the washer just in case.

Congrats to grahamcol for the best answer!

The tech guys got a code thrown up which APPEARS to suggest that there is an open circuit somewhere between the washer bottle and the coolant tank. They didn't have the tools to take it any further so next stop is an auto-electrician.

They couldn't find a coolant leak, though, so that's one thing...

 

[Noddy 99]

So who saw THIS one coming? Not me, for a kick-off...

Took this to the auto-electrician who checked EVERYTHING but couldn't find a fault. As he was about to close the bonnet, he noticed that the cooling fan had been disconnected...

The guy who did my remap about a month ago had clearly disconnected the fan and then forgotten to connect it up again... This is what has been causing the dashboard light and the fault is now fixed.

As my wallet is £180 lighter from today, I'll be having words with the remap guy..