[Jb7734]

Hey guys! I bought a CPO 2021 M550 with 15k miles a few months ago I love the car except for one thing which is driving me crazy. When I first got it I noticed a sweet chemical kind of smell coming through the vents. I thought maybe it was from something the dealership used to clean the car and didn’t let it bother me. About a month after I got the car I got a low coolant warning and the main reservoir was nearly empty. I filled the tank and took it to the dealer. At this point I realized that sweet smell might be coolant getting in the vents somehow. The dealer couldn’t find any source of a leak and said it passed a pressure test. He also said the tech and the shop foreman couldn’t detect any coolant smell in the vents. Since then I’ve only had to top up the coolant once so if there is a leak it’s a pretty slow one. Meanwhile the coolant smell is really bothering me its affecting my nose, throat sometimes giving me a headache.

Has anyone else had this issue with a 2021 M550? I know on the earlier models the turbo lines often are the culprit but mine has the upgraded metal lines. If anyone has any ideas I would be very grateful!

[AP]

Coolant leaks are unfortunately quite common , not just on the 550 but across the range
Had the issue with my previous 540 and it was one of the reservoirs. Leak is very small but you get to that point when it will trigger the warning. Warm the car up and it goes away and then when it’s cold again, it pops up again as the levels are on the threshold of what prompts the warning

Obviously a sealed system so don’t accept from dealer that’s it’s normal, it should not leak at all

May be worth using a torch/flashlight to have a look around in the engine bay and see if you see any residue. Is the coolant cap ok? Lose or seal faulty?

As it’s under warranty , should get this fixed before you have to pay for it out of your own wallet

Can’t answer about the smell though

[Joe-BMW33]

Yeah, you have a small to medium size coolant leak which is most likely dripping on the valley pan from the turbo coolant lines and burning off and coming through the vents. If you are smelling it in the cabin, the leak is definitely large enough for the dealer to see. Happened to me. I was getting add coolant messages every few months. Dealer said it was normal, which we all know it is not normal for cars to consume coolant. Eventually, there was a smell from the vents that was burning my eyes and nose. Full updated coolant line kit installed under warranty. No issues since, and no coolant "consumption", lol.

[AP]

Out of interest, when did the new coolant lines come out? We’re they integrated in any cars new and if so , from when?

[Joe-BMW33]

Originally Posted by AP

Out of interest, when did the new coolant lines come out? We’re they integrated in any cars new and if so , from when?

I believe BMW acknowledged the problem and went from rubber to braided aluminum at the end of 2019. They did not extend the warranty on it like the thermostat and active grill, they should really have.

I am not positive when they stopped using rubber in production. I have seen plenty of LCI's like this with line issues.

[AP]

Ok thanks. They may have considered it cheaper to use up the old stock and deal with issues in warranty rather than get rid of and replace with new lines. Probably cheaper for them , esepicially if the lines fail after the warranty has expired….

I’m getting far to sceptical in my old age!

[adhrp]

Originally Posted by Joe-BMW33

I believe BMW acknowledged the problem and went from rubber to braided aluminum at the end of 2019. They did not extend the warranty on it like the thermostat and active grill, they should really have.

I am not positive when they stopped using rubber in production. I have seen plenty of LCI's like this with line issues.

This was done MY20 onward as far as I know. If I recall correctly, the technical manual for MY20 states the updated turbo coolant lines.

OP, I had a coolant expansion tank leak (common in the G30), which was replaced promptly under warranty. Try a different dealer. Do not accept "no leak".

[Jb7734]

Thanks for all the replies! I will try another dealer and hopefully get this sorted.

[Marc_911]

I had the same symptom, it was the coolant expansion tank.