Low coolant dash message...
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Joined: Aug 2016
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2014 E350
Low coolant dash message...
On our 2014 E350, I got the low coolant warning message on a cold morning startup in the garage. So I kill the engine and take a peek: it needed mere ounces to raise the level from where I still could see the coolant's level to the top. Here's my point: I did this very same thing a few years ago, like at least three years (likely more?!!) ago. I have zero leaks evident, oil is "clean" on the cap and dipstick (and at oil changes), no evidence anywhere that I can tell of coolant or its mixing with oil that I can witness ...so why is the level dropping? Thoughts?
Edward
Edward
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Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
small coolant leak
On our 2014 E350, I got the low coolant warning message on a cold morning startup in the garage. So I kill the engine and take a peek: it needed mere ounces to raise the level from where I still could see the coolant's level to the top. Here's my point: I did this very same thing a few years ago, like at least three years (likely more?!!) ago.
I have zero leaks evident, oil is "clean" on the cap and dipstick (and at oil changes), no evidence anywhere that I can tell of coolant or its mixing with oil that I can witness ...so why is the level dropping?
Thoughts?
Edward
I have zero leaks evident, oil is "clean" on the cap and dipstick (and at oil changes), no evidence anywhere that I can tell of coolant or its mixing with oil that I can witness ...so why is the level dropping?
Thoughts?
Edward
Your coolant circuit may simply be actively venting through the normal pathway.
This type of small loss can be considered standard. Keep refilling as needed.
You can prevent active leaking by removing stored heat that cause boil over at engine stops.
Last edited by CaliBenzDriver; Nov 25, 2025 at 06:53 PM.
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2014 E350
Yes, Cali, I am wondering why in a closed system, the level drops without "apparent" reason that I can discern. I guess venting makes sense, perhaps?
Fwiw, I'm an old car guy and avid backyard wrencher for decades (cars and motorcycles), and short of a real leak or gasket/engine malady, I have never had to top off the coolant in any car I've have owned (that didn't have some issue) throughout these many years. To be sure, I ain't calling it a "problem" in this MB in any way; as I said, the last time I got this dash message was many years back. I was just wondering if others have experienced such, and if there's a reason for it. Car has 133k miles on it btw, and runs as strong and smooth as ever.
Edward
Fwiw, I'm an old car guy and avid backyard wrencher for decades (cars and motorcycles), and short of a real leak or gasket/engine malady, I have never had to top off the coolant in any car I've have owned (that didn't have some issue) throughout these many years. To be sure, I ain't calling it a "problem" in this MB in any way; as I said, the last time I got this dash message was many years back. I was just wondering if others have experienced such, and if there's a reason for it. Car has 133k miles on it btw, and runs as strong and smooth as ever.
Edward
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Coolant Leak sources
Yes, Cali, I am wondering why in a closed system, the level drops without "apparent" reason that I can discern. I guess venting makes sense, perhaps?
Fwiw, I'm an old car guy and avid backyard wrencher for decades (cars and motorcycles), and short of a real leak or gasket/engine malady, I have never had to top off the coolant in any car I've have owned (that didn't have some issue) throughout these many years. To be sure, I ain't calling it a "problem" in this MB in any way; as I said, the last time I got this dash message was many years back. I was just wondering if others have experienced such, and if there's a reason for it. Car has 133k miles on it btw, and runs as strong and smooth as ever.
Edward
Fwiw, I'm an old car guy and avid backyard wrencher for decades (cars and motorcycles), and short of a real leak or gasket/engine malady, I have never had to top off the coolant in any car I've have owned (that didn't have some issue) throughout these many years. To be sure, I ain't calling it a "problem" in this MB in any way; as I said, the last time I got this dash message was many years back. I was just wondering if others have experienced such, and if there's a reason for it. Car has 133k miles on it btw, and runs as strong and smooth as ever.
Edward
My M276 smell coolant since it's first Mile so I got used to the idea coolant must be going somewhere so I can smell it.
It's either normal discharge from tank or often the radiator plastic end craimps start leaking before the vent cap has a chance to open.
Bank2 rear coolant hoses gradually develop cracks to leak as engine mounts increasingly shake.
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2014 E350
Thanks for that feedback, man! Good to know ...especially about the engine mounts. So far at around 130k miles, the car is shake-free. A bit OT to this thread, but I've heard/read about these cars' mounts getting wonky at age so it's worth poking my head in there.
Edward
Edward
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W212 MY'14 M276-3.5NA @75kMi
heat as enemy
Thanks for that feedback, man! Good to know ...especially about the engine mounts. So far at around 130k miles, the car is shake-free. A bit OT to this thread, but I've heard/read about these cars' mounts getting wonky at age so it's worth poking my head in there.
Edward
Edward
Engine has a tendency to get extra hot.
Pay attention the your engine fan this winter to see if it keeps running regardless of cool weather.
Try to keep your engine oil clean on 5k.Mi schedule instead of annual.
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W212
how small is considered standard?
my level also keeps dropping about 5% per year (500ml out of 10L). im talking about om651 engine. the weird thing is, there is no leak. also pressure tested and everything was fine...
oil cooler, fuel filter housing and thermostat (with temp sensor included) were changed this year and the other.
sometimes i do get a cooland hot warning on my dash while driving, the coolant temp seems to jump to 100 something degrees celsius, and fan kicks in with max speed for a few seconds. if temp really gets over 100 degrees celsius, im thinking maybe the water from the coolant evaporates since its over boiling point? but shouldnt the coolant raise this boiling point though?
i dont understand why the level drops, even if just a little over the course of a year.
and temp fluctuation and max speed fan i also dont understand, there are no errors
my level also keeps dropping about 5% per year (500ml out of 10L). im talking about om651 engine. the weird thing is, there is no leak. also pressure tested and everything was fine...
oil cooler, fuel filter housing and thermostat (with temp sensor included) were changed this year and the other.
sometimes i do get a cooland hot warning on my dash while driving, the coolant temp seems to jump to 100 something degrees celsius, and fan kicks in with max speed for a few seconds. if temp really gets over 100 degrees celsius, im thinking maybe the water from the coolant evaporates since its over boiling point? but shouldnt the coolant raise this boiling point though?
i dont understand why the level drops, even if just a little over the course of a year.
and temp fluctuation and max speed fan i also dont understand, there are no errors
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Out Of Control!!
Joined: Apr 2019
Posts: 11,924
Likes: 6,776
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
extremely hot engines
how small is considered standard?
my level also keeps dropping about 5% per year (500ml out of 10L). im talking about om651 engine. the weird thing is, there is no leak. also pressure tested and everything was fine...
oil cooler, fuel filter housing and thermostat (with temp sensor included) were changed this year and the other.
sometimes i do get a cooland hot warning on my dash while driving, the coolant temp seems to jump to 100 something degrees celsius, and fan kicks in with max speed for a few seconds. if temp really gets over 100 degrees celsius, im thinking maybe the water from the coolant evaporates since its over boiling point? but shouldnt the coolant raise this boiling point though?
i dont understand why the level drops, even if just a little over the course of a year.
and temp fluctuation and max speed fan i also dont understand, there are no errors
my level also keeps dropping about 5% per year (500ml out of 10L). im talking about om651 engine. the weird thing is, there is no leak. also pressure tested and everything was fine...
oil cooler, fuel filter housing and thermostat (with temp sensor included) were changed this year and the other.
sometimes i do get a cooland hot warning on my dash while driving, the coolant temp seems to jump to 100 something degrees celsius, and fan kicks in with max speed for a few seconds. if temp really gets over 100 degrees celsius, im thinking maybe the water from the coolant evaporates since its over boiling point? but shouldnt the coolant raise this boiling point though?
i dont understand why the level drops, even if just a little over the course of a year.
and temp fluctuation and max speed fan i also dont understand, there are no errors
Far from alone with shared concern!
It's not your VIN, in fact it's not your engine type... many Diesels and gasers are impacted the way. It's a modern engine design that forces heat to higher limits.
Loosing half a Liter (nearly half a quart) per year is "normal" for a pressure-vented nearly sealed circuit. It should never vent but it always does.
No need to spend a fortune in new parts to cut that in half using a conventional way. Lowering stored heat is the key because system is forced to vent pressure from higher heat level.
Coolant losses happen after engine stop when stored pistons heat over boils the coolant circuit no longer circulating.
This setup is not a mystery - Be curious... : use a scanner to read the engine coolant sensor (ECT from ECU) at engine stop and for 20mn afterwards.
The high engine piston heat is not captured, contained nor removed by the coolant nor oil while driving. The stock setup stores extreme heat in dry non-spray cooled pistons.
The engine fan keeps spinning high in winter, unable to remove stored heat. The Temp IC display is known to be doctored for looks.
Yes it is pushing limits, yes it does work.
Try to keep your diesel/gas engine oil clean on 5k.Mi schedule.
Newer Bosch controls on Mercedes and GM's feature a radiator shutter to stop all air flow so max heat is reached above 100°C...
I've experimented circulating pistons heat out to find ...:
- Cooling fan stops in 100°F summer!
- Coolant heat soaks stopped
- Oil stopped vaporizing out
- sealed cylinders stopped vibrating
- tranny stopped shifting erratically
I call that heat removal "MOD-X"... some ppl dislike non-stock oil, some ppl enjoy what it does, others ignore it.
Last edited by CaliBenzDriver; Nov 27, 2025 at 02:46 PM.
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Out Of Control!!
Joined: Apr 2019
Posts: 11,924
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
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W209
IF you have coffe with milk, then you may have a problem
Out Of Control!!
Joined: Apr 2019
Posts: 11,924
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
blue + turquoise
I wonder what kind of milk shake these two would make ?
Last edited by CaliBenzDriver; Dec 2, 2025 at 12:03 AM.
