[paulyboy123]

So about 4.5 weeks ago I had a low coolant warning on my 2020 M5 Comp (8800 miles). I had filled up around a cups worth of coolant to the main reservoir and the other reservoir was normal level. Come to think again the warning did go away when I shut the car off and started it back up although the level was indeed low and way below the minimum mark. Now fast forward to today I got the warning again and had restarted the car and the warning went away, upon checking regardless the coolant was indeed again way below the minimum line and this time about a cup and a half's worth of coolant was added to bring it up between the max and min line. After driving it to operating temps I had parked it back home in the drive way and noticed the coolant was on the ground and checked the levels and they were now way above maximum meaning it had been seemingly overfilled and the excess coolant was dumped. What I am not understanding is where the coolant is going to begin with that is making levels drop like this and why restarting the car makes the warning go away although checking it confirms that it is low. Today's situation seemed to result in it being overfilled although it was never above max line. I cannot find a single leak anywhere within the engine although there does seem to be a sweet smell coming from it when it is running. Also to note I am on the NYC area and the weather has been getting a little colder so that may affect levels but I don't assume to this extent. The picture attached is taken after driving showing that the levels were now above max although being filled originally to between the min and max levels.

[SigForLife]

There is an issue (with a related bulletin, I understand) with a plug on the top of the engine not sealing. They just had to replace mine because I got a low coolant light and they were able to find coolant leaking in the plug area.

[paulyboy123]

Originally Posted by SigForLife

There is an issue (with a related bulletin, I understand) with a plug on the top of the engine not sealing. They just had to replace mine because I got a low coolant light and they were able to find coolant leaking in the plug area.

Which plug are you referring to?

[SigForLife]

I don’t know. I’m going off what my dealer told me. It was difficult to get to, as I understand it but, as I mentioned, there is a related bulletin to it

[WayneM3]

My 2019 is definitely losing coolant too as I have the smell and there is residue around the edge of the coolant tank but I am unable to tell where it is coming from. The top is on as tight as it goes (the arrows line up) but seems not to be all that tight compared to my previous BMW's. I am curious about this service bulletin.

[SenorFunkyPants]

My SA reckoned that a single low coolant warning when the weather turns cold is quite common across the BMW range.
Though you think BMW would factor in expansion/contraction in the coolant system.

[paulyboy123]

Originally Posted by SenorFunkyPants

My SA reckoned that a single low coolant warning when the weather turns cold is quite common across the BMW range.
Though you think BMW would factor in expansion/contraction in the coolant system.

I agree, when I got it the first time I didn't think much of it as the weather was indeed changing. But now the warning is back within a month? Something is up I believe. Glad to hear though that I am not the only person. I also do think that it is the cap that it may be evaporating through since I do see residue on the outside threading that looks like coolant.

[paulyboy123]

Originally Posted by WayneM3

My 2019 is definitely losing coolant too as I have the smell and there is residue around the edge of the coolant tank but I am unable to tell where it is coming from. The top is on as tight as it goes (the arrows line up) but seems not to be all that tight compared to my previous BMW's. I am curious about this service bulletin.

Are you smelling it from the exhaust or the engine bay? My engine bay has a sweet sort of smell, but my exhaust smells smells normal.

[WayneM3]

The smell is only from the engine compartment - not the exhaust. You can see the residue here.

[paulyboy123]

Going to update this thread, I have a service appointment at my dealership to hopefully get this checked out. Also noticed that the weird smell of the coolant comes apparent after it reaches around operating temperature (210F). Smell comes from the driver side of the engine bay.

[HerkHealer]

This happens on the M550 also.
I've had my 2020 in twice for it already. They say "pressure checked system, no leak".
My low coolant warning came on twice within 1,000 miles that is NOT normal BMW!

[paulyboy123]

Originally Posted by HerkHealer

This happens on the M550 also.
I've had my 2020 in twice for it already. They say "pressure checked system, no leak".
My low coolant warning came on twice within 1,000 miles that is NOT normal BMW!

Yup not sure on the issue, can't find a leak but can definitely smell something when the engine is operating temp. It's definitely leaking somewhere so for now I'll just keep filling it as needed until my appointment.

[WayneM3]

I stopped at the BMW dealer yesterday because I was next door and decided to show it to the service advisor in person instead of just in pictures and when I popped the hood, it was spurting out right in front of us - like a pinhole leak! I did not see for sure if it was coming from the 2 hoses that pass over it or from the reservoir but I thought it was the reservoir and he thought it was the hoses. Needless to say, they did not have a loaner car available yesterday so I brought it back today and got the loaner car. We'll see soon what they come back and say was the issue but it had better not be "no leak" as we both saw (and I think he got a picture of) it leaking.

[paulyboy123]

Dropped my M5 off today at the dealer and was provided a 2021 330i as a loaner(you would think they would give at least a 5 series!) SA told me it would be a day before they look at it because they are down 3 techs. Hopefully quick turnaround and they find the issue instead of brushing it off as a regular thing. Ironically this morning before I set off to head there I got a low coolant warning again upon start up!

[paulyboy123]

Well I just got my car back today, they told me they couldn't find any leaks and preformed a pressure test. Tech told me the way these engines are build they run very hot and the location of the coolant tanks causes it to burn coolant faster than other BMW cars. Also he noted it could be air in the system that didn't properly bleed out the first time causing levels to fluctuate therefore triggering a low coolant warning. Don't know if what he told me is true or not but I will keep an eye on the car. They also provided a whole bottle of coolant free of charge.

[BobsM3Coupe]

Originally Posted by paulyboy123

Well I just got my car back today, they told me they couldn't find any leaks and preformed a pressure test. Tech told me the way these engines are build they run very hot and the location of the coolant tanks causes it to burn coolant faster than other BMW cars. Also he noted it could be air in the system that didn't properly bleed out the first time causing levels to fluctuate therefore triggering a low coolant warning. Don't know if what he told me is true or not but I will keep an eye on the car. They also provided a whole bottle of coolant free of charge.

Tech said these cars burn coolant? Sounds like a visit to another dealer is in order. Have the tech go back to Pep Boys.

[paulyboy123]

Originally Posted by BobsM3Coupe

Tech said these cars burn coolant? Sounds like a visit to another dealer is in order. Have the tech go back to Pep Boys.

Thought the same thing, whatever I'll keep an eye on it for now and have proof that he stated that. If it comes up again very quick I will be scheduling an appointment with another dealer.

[HerkHealer]

Originally Posted by BobsM3Coupe

Tech said these cars burn coolant? Sounds like a visit to another dealer is in order. Have the tech go back to Pep Boys.

My 2020 M550 is losing coolant constantly. I've had 2 low coolant warnings pop up on I Drive within 1,000 miles driven. It's ridiculous.

I constantly complain of coolant smell when I park in garage and even a highly toxic burning smell when driving for 30 mins or more from the coolant burning up. Same thing every time. These V8 engines do this. They point out the 10,000 mile service to check and refill the coolant level.

I bring it in, they "pressure test" the system and clean the "V" area of the engine and say everything is fine.

Its so damn frustrating.

[N-Dorfin]

Typically the leak of the cooling fluid on m5 f90 can cause this:

1) if is a new car - the cooling system needs to "expand", it can take up to 1l of cooling fluid to be added within a short period of time ... if consumption of cooling fluid won't stop then it is

2) bad top cap of cooling fluid tank - bad design of the cap and high pressure of cooling system cause occasionally bursts of cooling fluid into engine area - typically sign are white spots on the engine cover and surrounding area (BMW knows about this and SA are advised to change this part)

IMPORTANT! the bursts can cause following - cooling fluid bursts into spark plugs and coil area causing corrosion of coils - engine can then start falling into "safety mode/limb mode" under certain load and diagnostics of your SA says there are misfires at certain valves .. all that is because of the corrosion of the coils - solution is to change the cap of cooling fluid tank, change coils and spark plugs and clean the area (had this problem on my M5 and few other guys here as well)

3) It can be also caused by a broken radiator - since all front radiators are quite unprotected, a small stone from the car in front of you could hit the radiator .. then it is important to check from which tank is cooling fluid leaking (if the engine one or the one for turbos) ... an indicator of this could also be a pond under your car .. solution is to take it to your SA to pressure the cooling system .. since you wrote you already did it, the solution is probably 1) or 2)

Interesting fact:
preLCI M5 operates at 120°C whether LCI runs at 100°C .. I guess guys at BMW realized there is a problem with high temperature and high pressure in the cooling system ...

Cheers,
Petr

[paulyboy123]

Originally Posted by N-Dorfin

Typically the leak of the cooling fluid on m5 f90 can cause this:

1) if is a new car - the cooling system needs to "expand", it can take up to 1l of cooling fluid to be added within a short period of time ... if consumption of cooling fluid won't stop then it is

2) bad top cap of cooling fluid tank - bad design of the cap and high pressure of cooling system cause occasionally bursts of cooling fluid into engine area - typically sign are white spots on the engine cover and surrounding area (BMW knows about this and SA are advised to change this part)

IMPORTANT! the bursts can cause following - cooling fluid bursts into spark plugs and coil area causing corrosion of coils - engine can then start falling into "safety mode/limb mode" under certain load and diagnostics of your SA says there are misfires at certain valves .. all that is because of the corrosion of the coils - solution is to change the cap of cooling fluid tank, change coils and spark plugs and clean the area (had this problem on my M5 and few other guys here as well)

3) It can be also caused by a broken radiator - since all front radiators are quite unprotected, a small stone from the car in front of you could hit the radiator .. then it is important to check from which tank is cooling fluid leaking (if the engine one or the one for turbos) ... an indicator of this could also be a pond under your car .. solution is to take it to your SA to pressure the cooling system .. since you wrote you already did it, the solution is probably 1) or 2)

Interesting fact:
preLCI M5 operates at 120°C whether LCI runs at 100°C .. I guess guys at BMW realized there is a problem with high temperature and high pressure in the cooling system ...

Cheers,
Petr

Wow thank you for the super detailed list. I believe the problem is 2 but I will keep an eye on it now. I won't be touching the cap or anything. Just praying it doesn't give me a warning again haha.

[HerkHealer]

Originally Posted by N-Dorfin

2) bad top cap of cooling fluid tank - bad design of the cap and high pressure of cooling system cause occasionally bursts of cooling fluid into engine area - typically sign are white spots on the engine cover and surrounding area (BMW knows about this and SA are advised to change this part)

Cheers,
Petr

Not in the States, or at my Dealership. I brought by M550 in and sent pics of dried up white powdery stuff all over the cap area. I even specifically mentioned wanting my cap replaced. He told me that they "pressure" tested everything and all is OK. I ended up buying a new cap myself for $23 (i think). It was not much, but BMW needs to address this. Like I said earlier, i had a Low Coolant warning come on TWICE within 1,000 miles driven. Both times they filled it back up, cleaned the "V" area of my engine and pressure tested. Says its fine. Its NOT fine. I will keep bringing it back again, and again, and again........dont care what they say.

[pbonsalb]

Has the new cap fixed the leak? As I understand some early cars with the 100C thermostat and some later cars with the 90C thermostat have the problem. Still, I bought a 90C tstat to install for whatever it is worth.