Coolant warning still comes on

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Jan 20, 2023 | 01:45 PM

cahaba

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2018 GLS 450

Coolant warning still comes on

I have a 2018 GLS 450 with 44K miles. I recently got 'Check Coolant Level' warning message. I went ahead and did a coolant flush (flush & replace) at a local Indy shop. However, the coolant warning still flashes up in my car. It has been 3-4 days since I changed the coolant and have also turned on heat / defogger to maximum and drove for around 50 miles since the coolant work was done.

Any ideas on what may be going on?

Thanks!

Jan 20, 2023 | 02:29 PM

WillieMack

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Mayback

Quote:

Originally Posted by cahaba

there is a secondary coolant tank underneath the engine cover. Also the sensor for the primary coolant tank is pretty high up to the top so you may need to add all the way up closer to the top because if it’s just a hair off off that sensor the light will still come on. I had same issue on my GLS550 even after my Indy added coolant. Took it to dealer and they said needed to add more so that the coolant is up to the top hitting the sensor.

Jan 20, 2023 | 03:11 PM

cahaba

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2018 GLS 450

Thanks!!!
Didn't knew about the second coolant tank. I will check into it and also check the level in primary tank. Will keep you posted.

Feb 7, 2023 | 06:31 PM

cahaba

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2018 GLS 450

Is the highlighted the correct second coolant tank? Just want to make sure. Thanks!

Feb 8, 2023 | 09:05 AM

threeMBs

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Feb 9, 2023 | 06:44 PM

cahaba

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2018 GLS 450

Thanks @WillieMack and @threeMBs. Appreciate all your help.
I did top off the second coolant tank; let' see if that takes care of the low coolant warning.

Feb 15, 2023 | 06:42 PM

cahaba

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2018 GLS 450

The coolant warning / message is still present even after I topped off both coolant tanks. Both of these tanks were pretty full, brimming almost to the top -- even before I topped them.

Any ideas on what may be going on here? Is there a sensor that needs to be looked into?

Thanks.

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Feb 17, 2023 | 10:04 PM

John CC

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From: New Hampsha

'17 GLS450, '14 GLK250, Grandpa's Roadster

Quote:

Originally Posted by masscomguru

I get the coolant warning only at start up if the car sits outside in cold weather.

That's actually not that uncommon. It usually means the coolant level is right at the trigger level. Warm it up a little and it expands enough to shut the light off.

As to OP's problem, these systems used to be stone simple: a float closes a switch when the level drops and the light comes on. Whether they're that simple these days, who knows, probably not, but you could always try unplugging the sensor, if you can find it, and see what happens.

Feb 18, 2023 | 03:13 PM

#10

Eonetiller

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Joined: Jun 2014

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From: NJ

2018 GLS550

Quote:

Originally Posted by masscomguru

2018 here as well, same story with the cold weather. I only have the warning when I'm parked in my steep driveway and the overnight temp is below 30 degrees F

Last edited by Eonetiller; Mar 20, 2023 at 09:16 PM.

Mar 17, 2023 | 12:05 PM

#11

cahaba

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2018 GLS 450

My coolant warning problem has been resolved. As far as I can tell -- it was due to unusual reason: driveway where my car is parked overnight has a upward gradient slope of about 5%. And in the winter I think the coolant condensed so that the coolant level dipped below the sensor, and gave low coolant warning. Once I filled the coolant to the top of the cap (more than the max allowed level) -- the issue got resolved. Not sure if filling more than recommended level is a good practice in the long run though.