[desert_rain]

Hi all.

I have 2017 440i with b58. In last two weeks when I park and coming back in short period -which means engine is still hot- when I start the engine, burnt smell comes from vents for a short period, only at beginning and not always.

Is it indicator of leak or problem?

[Tommy-G]

I have a similar issue. My E93 did it as well. It is apparently a valve cover gasket or rear main seal.

I was very upset that my new (to me) F33 is starting to do the same thing.

[Desertnate]

Is it really a mechanical problem?

One thing I've noticed in many cars is this time of year is when the heater kicks in and runs hotter than it has for several months, you get a burning-like smell I always attributed to dust and lint "cooking" somewhere in the HVAC system. It usually goes away fairly quickly after restarting each time and after a few days of cold weather it goes away completely.

[Billfitz]

Yep, dust etc that's built up in the heater core over the summer will smell when you first blow air through the heater core to warm the car. The forced air furnace in my house does the same thing. After a few cycles it goes away. Or it could be a dead mouse in your heater...

[dmaxdmax]

I'm sure it's a dead mouse...maybe try sucking it out of the top center vents with a wet/dry vac?

...and although I agree it's just the heater not being used for a while, you should get to know your smells. Burned oil is different smelling and tasting than coolant.

If you are smoking when idling at a light and smell it inside the cabin, valve cover is a decent bet, unless you had the oil changed by morons.

You can put the fan up to high and take it out for a nice highway drive with a couple of windows open to suck all the dust/dead mice bits out. I do that after riding with gf's hairy dog.

[Tommy-G]

Originally Posted by dmaxdmax

I'm sure it's a dead mouse...maybe try sucking it out of the top center vents with a wet/dry vac?

...and although I agree it's just the heater not being used for a while, you should get to know your smells. Burned oil is different smelling and tasting than coolant.

If you are smoking when idling at a light and smell it inside the cabin, valve cover is a decent bet, unless you had the oil changed by morons.

You can put the fan up to high and take it out for a nice highway drive with a couple of windows open to suck all the dust/dead mice bits out. I do that after riding with gf's hairy dog.

I just drop the top and only have to smell all the Floridians smoking weed on the roads

[HarryTee]

Originally Posted by dmaxdmax

I'm sure it's a dead mouse...maybe try sucking it out...

[desert_rain]

Thanks guys! I dont’t do anythink for now. Also I did’n smell anything today. Maybe mause is cooked already btw it smells like burned oil or plastic.

dmaxdmax I bought this car 3 months ago. I had 2017 430 xdrive before this 440 but it was stolen, unfortunately. I don’ t know what previous owner did. BMW did check to car when I was buying and they said car is ok.

[dmaxdmax]

So maybe you should take some oil and burn it with a lighter in a teaspoon...same thing with plastic.

They'll have different smells. Burning plastic is an issue. Burning oil is one too, but it's expected with every car at some point.

If you didn't smell it today, perhaps its because of your drive. If it's the valve cover gasket, you'd notice the burning after you're at operating temp and stopped at a light...the smoke will come into the cabin. If you pull over when you smell this and open the hood, look along the exhaust side of engine for smoke.

When cold, rub your finger under valve cover...if you have oil on it, you have a leak.

I haven't done a b58 valve cover gasket but the plugs were easy to do, so I'm expecting to need to do it soon.

Anyway, know your smells. Burning plastic is not a usual smell...would indicate something electrical isn't right...I would guess.

[DelawareBMW]

I have a F32 Sportline Coupe that had the same exact issues your speaking of. I literally thought I was smelling musty dust but it was very faint and only occured right after inital startup and sometime when I would have the car idling sitting still in a parking lot or drive-thru line. I would start the car and randomly smell the faintest smell of something but I couldn't put my finger on it. It wasn't until a month or two later the I got a random Low Coolant Warning so I went to check for visible leaks and puddle but didn't notice any so I just filled her back up and went about my life

Roughly two months later the same warning popped up. So this time I decided to dig a little deeper. What I found was that my Coolant Expansion Tank had an ultra slow leaking near the electrical plug at the bottom of the tank (which is used for the coolant level sensor inside the tank). The easiest way to view this is by tanking off the front wheel well cover on the side of your coolant tank.

Upon replacing my tank (roughly $125 DIY repair) I noticed the thin hose which runs above the radiator and connects to the top of that tank had a hairline crack. There was no visible leaking there but when I removed the hose to replace the tank the hose literally crumbled in my fingers near the joints on both sides. Long story short it was a blessing in disguise because the would have me stranded on the side of the road within the next 15-25k miles.

I highly recommend anyone with a 3 ir 4 series in this generation to replace the "coolant expansion tank hose" that connects to the top of your coolant tank once the car hits 40k (or beyond). All the heating and cooling of the engine bay and internal fluid that runs through that hose cause it to get very frail. Its a $25-$40 ultra simple repair that will save you hundreds if not thousands in repair/towing down the line. It appears to be a common pain point on these cars and its that second modern BMW that I've owned to have had this issue. Coolant will have a distinctive smell. Its somewhat musty and slightly sweet. If it gets bad enough to show visble smoke its usually a clear/light colored. Many times the smell will come weeks to months before you see any smoke.

There is also an issue in some of the F30, 31, 32's where condensation builds up from the cars heating/cooling This condensation will smell musty like mildew since it essentially gets trapped. This problem hasn't happened to me personally but I stumbled onto it when I was researching my own faint smell. I'm fairly certain BMW issued a service bulletin on this but don't quote me on that as I only read it trying to solve my own issue.

Other then this minor hiccup this 435i Sportline Coupe has been rock solid reliability-wise.

Best of luck!

[CrumbyButter]

Originally Posted by DelawareBMW

I have a F32 Sportline Coupe that had the same exact issues your speaking of. I literally thought I was smelling musty dust but it was very faint and only occured right after inital startup and sometime when I would have the car idling sitting still in a parking lot or drive-thru line. I would start the car and randomly smell the faintest smell of something but I couldn't put my finger on it. It wasn't until a month or two later the I got a random Low Coolant Warning so I went to check for visible leaks and puddle but didn't notice any so I just filled her back up and went about my life

Roughly two months later the same warning popped up. So this time I decided to dig a little deeper. What I found was that my Coolant Expansion Tank had an ultra slow leaking near the electrical plug at the bottom of the tank (which is used for the coolant level sensor inside the tank). The easiest way to view this is by tanking off the front wheel well cover on the side of your coolant tank.

Upon replacing my tank (roughly $125 DIY repair) I noticed the thin hose which runs above the radiator and connects to the top of that tank had a hairline crack. There was no visible leaking there but when I removed the hose to replace the tank the hose literally crumbled in my fingers near the joints on both sides. Long story short it was a blessing in disguise because the would have me stranded on the side of the road within the next 15-25k miles.

I highly recommend anyone with a 3 ir 4 series in this generation to replace the "coolant expansion tank hose" that connects to the top of your coolant tank once the car hits 40k (or beyond). All the heating and cooling of the engine bay and internal fluid that runs through that hose cause it to get very frail. Its a $25-$40 ultra simple repair that will save you hundreds if not thousands in repair/towing down the line. It appears to be a common pain point on these cars and its that second modern BMW that I've owned to have had this issue. Coolant will have a distinctive smell. Its somewhat musty and slightly sweet. If it gets bad enough to show visble smoke its usually a clear/light colored. Many times the smell will come weeks to months before you see any smoke.

There is also an issue in some of the F30, 31, 32's where condensation builds up from the cars heating/cooling This condensation will smell musty like mildew since it essentially gets trapped. This problem hasn't happened to me personally but I stumbled onto it when I was researching my own faint smell. I'm fairly certain BMW issued a service bulletin on this but don't quote me on that as I only read it trying to solve my own issue.

Other then this minor hiccup this 435i Sportline Coupe has been rock solid reliability-wise.

Best of luck!

Any idea what the part # is on that expansion tank hose? Are you replacing with OEM or aftermarket or doesnt really matter?