Sudden coolant warning
Thread Starter
Junior Member
Joined: Aug 2022
Posts: 26
Likes: 1
‘12 S550
Sudden coolant warning
Hi all, suddenly got this coolant warning. The coolant was flushed and topped off about two months ago. I drove the car around after dismissing the warning for a few hours and the operating temperature stayed at 89C which it has always stayed at. Is this an urgent issue? And what is the worst possible scenario?
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,322
Likes: 1,678
S500
when you get a warning of this nature - the correct thing is to validate the message, its never to just continue the journey
a replacement engine is going to be (depending on specific one you have) the wrong side on $10K and at least two weeks minimum without your car, never mind being stuck somewhere for a few hours etc.
So the first thing ought to be to Stop and verify it
1) the coolant bottle is full
2) the top hose full of coolant and when you repeatedly squash the hose you feel vast quantities of coolant moving and not air (don't stick hands in fans or drive belts - turn things off)
3) there is no visible white patches all over the engine and engine bay (of cooked antifreeze that's leaked and dried out)
4) that there are no visible traces of coolant leaking out
5) check engine oil level and colour
that list is a few sensible steps, that take much less than 5 minutes at the roadside - if these come back normal, proceed gently, monitoring gauges, other warning messages, and engine behaviour and smell. An over heating engine will feels slightly under powered, will have a funny erratic idle and start to smell hot and bothered and may stall with low load.
Once the coolant level is depleted, the reading of the engine temp gauge can no longer be relied upon, there may be no coolant around the sensor to give the correct reading
as there was work done and the things are hard to get the coolant around and all the air out - it might be trapped air - or a sensor failure - but driving on is a recipe for wasting time (not saving time) and can empty your wallet unnecessarily
a replacement engine is going to be (depending on specific one you have) the wrong side on $10K and at least two weeks minimum without your car, never mind being stuck somewhere for a few hours etc.
So the first thing ought to be to Stop and verify it
1) the coolant bottle is full
2) the top hose full of coolant and when you repeatedly squash the hose you feel vast quantities of coolant moving and not air (don't stick hands in fans or drive belts - turn things off)
3) there is no visible white patches all over the engine and engine bay (of cooked antifreeze that's leaked and dried out)
4) that there are no visible traces of coolant leaking out
5) check engine oil level and colour
that list is a few sensible steps, that take much less than 5 minutes at the roadside - if these come back normal, proceed gently, monitoring gauges, other warning messages, and engine behaviour and smell. An over heating engine will feels slightly under powered, will have a funny erratic idle and start to smell hot and bothered and may stall with low load.
Once the coolant level is depleted, the reading of the engine temp gauge can no longer be relied upon, there may be no coolant around the sensor to give the correct reading
as there was work done and the things are hard to get the coolant around and all the air out - it might be trapped air - or a sensor failure - but driving on is a recipe for wasting time (not saving time) and can empty your wallet unnecessarily
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MBWorld Fanatic!
Joined: Nov 2014
Posts: 1,560
Likes: 207
From: Maryland
Depends on the weather
Depends on where you do it. The water pump directly from MB is $549 plus if you do the thermostat, gaskets etc., dealer is probably going to charge you around 1500-2kish. If you go the dealer route, make sure they don't jack up the price on parts. You can call the parts dept and order them directly and have the dealer install them or order the stuff directly from MB online. Sounds like you can't DIY or have any indy as an option?
Thread Starter
Junior Member
Joined: Aug 2022
Posts: 26
Likes: 1
‘12 S550
Depends on where you do it. The water pump directly from MB is $549 plus if you do the thermostat, gaskets etc., dealer is probably going to charge you around 1500-2kish. If you go the dealer route, make sure they don't jack up the price on parts. You can call the parts dept and order them directly and have the dealer install them or order the stuff directly from MB online. Sounds like you can't DIY or have any indy as an option?
Super Member
Joined: Dec 2018
Posts: 857
Likes: 501
From: Washington, DC
2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
So my S600 water pump story is similar. I had a slow leak causing the yellow light to pop on. I also had a chirp (like a bird chirping) in the serpentine belt. Turned out one of the water pump bolts was missing. I had them replace the water pump, the belt, the idler pulleys, the top and bottom hoses, and that short vertical hose behind everything along with all new blue coolant.
The dealer did the work. I had a warranty and it covered about $950 against a $1600 bill. No leaks at all since then. I wanted to keep the car long term. If it was just a flip car, I would have stuck a new bolt in that water pump and tightened the hell out of everything to slow the leak enough to sell it.
The dealer did the work. I had a warranty and it covered about $950 against a $1600 bill. No leaks at all since then. I wanted to keep the car long term. If it was just a flip car, I would have stuck a new bolt in that water pump and tightened the hell out of everything to slow the leak enough to sell it.
