[vanos84]

I'm just on the verge of taking my car in for service to find out what the hell is burning under the hood. I figured I would check here first to see if anyone else has encountered this. The smell is ever present when I stop after a drive. It's especially strong after driving the car a bit harder. This smell is not that of oil burning or even rubber but to me smells like an electric motor that is fried or maybe even electrical wires burning. Honestly to me it smells eerily similar to what a ceiling fan motor smells like after it burns up. So the only thing I can think of is that the cooling fans are possibly going out, which would be the most concerning. Any ideas?

[micvite]

Originally Posted by vanos84

I'm just on the verge of taking my car in for service to find out what the hell is burning under the hood. I figured I would check here first to see if anyone else has encountered this. The smell is ever present when I stop after a drive. It's especially strong after driving the car a bit harder. This smell is not that of oil burning or even rubber but to me smells like an electric motor that is fried or maybe even electrical wires burning. Honestly to me it smells eerily similar to what a ceiling fan motor smells like after it burns up. So the only thing I can think of is that the cooling fans are possibly going out, which would be the most concerning. Any ideas?

Sounds to me like normal "hot engine smell"? It's really hard to tell as it couldn't be anything burning up if it is a problem or it could just be the smell of hot metal and stuff

[AHall]

Originally Posted by vanos84

I'm just on the verge of taking my car in for service to find out what the hell is burning under the hood. I figured I would check here first to see if anyone else has encountered this. The smell is ever present when I stop after a drive. It's especially strong after driving the car a bit harder. This smell is not that of oil burning or even rubber but to me smells like an electric motor that is fried or maybe even electrical wires burning. Honestly to me it smells eerily similar to what a ceiling fan motor smells like after it burns up. So the only thing I can think of is that the cooling fans are possibly going out, which would be the most concerning. Any ideas?

I would make the appointment and take it in to the dealership. How old is the car? I assume this just started.

[M5 F90 (2018)]

You sound like you know a hot burning/electrical smell when you smell it and suggest you get it checked asap. I would!

[vanos84]

Originally Posted by AHall

I would make the appointment and take it in to the dealership. How old is the car? I assume this just started.

It's the one that's listed in my sig. 18 model yr.

[shawnhayes]

I smelled this faintly for my 2018 at all times.

I also smell it in my CS during break in so far.

But it's "faint". Very small. If you have a change, get it checked.

Shawn

[vanos84]

Thanks for the replies, yeah it's pretty noticeable at times. When I park in the garage I can smell it coming through the ac vents.

[HerkHealer]

Originally Posted by vanos84

Thanks for the replies, yeah it's pretty noticeable at times. When I park in the garage I can smell it coming through the ac vents.

Might be the infamous "coolant leak" these V8s have. When coolant pools in the bottom of the V portion of the engine it smells awful. Its almost toxic and makes your eyes water and it smells like electrical burning. I've had it and several other M5/M550 owners as well. There is a TSB from BMW on how to clean the area. And dont worry, BMW will tell you its perfectly OK because they "pressure tested" the system and found no leaks.

My M550 has been in twice with low coolant errors on I Drive 7 within 1000 miles and they say its good to go because they pressure tested it.



P.S. - I was stationed at Warner Robins from 2003-2010

[SigForLife]

Originally Posted by HerkHealer

Might be the infamous "coolant leak" these V8s have. When coolant pools in the bottom of the V portion of the engine it smells awful. Its almost toxic and makes your eyes water and it smells like electrical burning. I've had it and several other M5/M550 owners as well. There is a TSB from BMW on how to clean the area. And dont worry, BMW will tell you its perfectly OK because they "pressure tested" the system and found no leaks.

My M550 has been in twice with low coolant errors on I Drive 7 within 1000 miles and they say its good to go because they pressure tested it.



P.S. - I was stationed at Warner Robins from 2003-2010

When my low coolant notice came on, my dealership said there was a notice about this (2020 M5 Comp) and promptly replaced a plug on the top of the engine and I haven’t had a problem since

[vanos84]

Originally Posted by HerkHealer

Might be the infamous "coolant leak" these V8s have. When coolant pools in the bottom of the V portion of the engine it smells awful. Its almost toxic and makes your eyes water and it smells like electrical burning. I've had it and several other M5/M550 owners as well. There is a TSB from BMW on how to clean the area. And dont worry, BMW will tell you its perfectly OK because they "pressure tested" the system and found no leaks.

My M550 has been in twice with low coolant errors on I Drive 7 within 1000 miles and they say its good to go because they pressure tested it.



P.S. - I was stationed at Warner Robins from 2003-2010

Cool, so you weren't too far. I actually love Warner Robins. I love going to the air shows at the base. The town itself is very nicely spread out. It's amazing how that town has grown since the early days. Which I'm sure you noticed a big change being there for those years!

[Pimpsy]

Expansion tank gasket leaking.

[AHall]

Originally Posted by Pimpsy

Expansion tank gasket leaking.

Tank gasket? Is that the tank cap or something else? Was it defective or did something else cause it to fail?

[Pimpsy]

Defective gasket, design, or assembly.
Coolant is leaking onto the coils and injectors, causing the burning smell and requiring replacement of those parts.
This happened to my 2019 M5C and my advisor said it's not uncommon.
It smelled like burning plastic, most evident when the car was still.

[AHall]

Originally Posted by Pimpsy

Defective gasket, design, or assembly.
Coolant is leaking onto the coils and injectors, causing the burning smell and requiring replacement of those parts.
This happened to my 2019 M5C and my advisor said it's not uncommon.
It smelled like burning plastic, most evident when the car was still.

The question has more to do if they performed a long term repair or you will be back for the same repair since they only replace a part prone to fail with another part prone fail.

[Pimpsy]

Originally Posted by AHall

The question has more to do if they performed a long term repair or you will be back for the same repair since they only replace a part prone to fail with another part prone fail.

Good question. I didn't perform the repair or inspect the failed parts so I can't answer that although this sort of problem should be able to be (more or less) permanently fixed.

I'll try to get more info the next time I see my service advisor, which will be soonish.

[BoneMendingWorker]

I've just started noticing a smell that sounds very similar to what you're describing. Mainly notice it when I pull in the garage after driving home from work. Initially thought it was the "hot engine smell", but it's recently become more prominent. I have a 2018 as well. 26k miles.

[jnotrom711]

I had the expansion tank leak, replaced under warranty, I didn't smell anything burning or melting smell with my f90. However with my f10 M5, I did have a burning, hot electrical smell. Brought it in, and tech told me something about one of the battery cables. I dont recall which one, but he mentioned it was not the first time he saw it. Where someone put in a new battery and didnt attach something properly, and it was causing some sort of short that didnt affect drive-ability, however when inspecting the battery cable, one of them was definitely melted and burned. He said he's seen several car fires from this. Luckily for me they just replaced the cable, new battery, and on my way. He made it sound like a simple error whoever installed the battery made. Either loose, or something touching it, not sure. Try inspecting the battery cables if the expansion tank doesnt fix it.