# Is This Normal?



## rmorin49 (Jan 7, 2007)

This is the second time my car has exhibited this behavior: 
Pull up in the driveway and shut down the engine.
Fan continues to run and there is a burning oil type of smell emanating from the engine compartment, no smoke, just a smell.
Fan runs for about 5-10 minutes and then shuts down. It did this about a week ago after a short drive and then again this evening after my 25 mile commute home from work. 
Am I crazy, is this normal or do I have a problem? There are no warning lights and the car runs great. Thanks for the help.


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## cssnms (Jan 24, 2011)

Sounds like particulant burn-off, if so, it's normal.


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## F32Fleet (Jul 14, 2010)

Normal. The smell decreases as time goes on.


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## bayoucity (Jun 11, 2010)

It's normal as long as it happens infrequently.


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## rmorin49 (Jan 7, 2007)

Thanks, folks. I feel better now, back to watching my favorite TV show, NCIS.


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## bimmerdiesel (Jul 9, 2010)

reminds me of my fan experiences when I got it. I used to stand right there till it would stop. I knew its was DPF through forums but I anxiety was soo much initially


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## rmorin49 (Jan 7, 2007)

bayoucity said:


> It's normal as long as it happens infrequently.


Twice since 3/27 and 800 miles.


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## bayoucity (Jun 11, 2010)

I don't believe you have anything to worry about as I can recall it happens about 5-6 times during my 9 months ownership. Lots of folks are saying it has to do with diesel particulate burn off or something to that nature. Again, I spend approximately 15 miles on highway daily to & from my office which means there are plenty of chances for burn off to occur without knowing it because the vehicle is cruising on the freeway.


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## rmorin49 (Jan 7, 2007)

bayoucity said:


> I don't believe you have anything to worry about as I can recall it happens about 5-6 times during my 9 months ownership. Lots of folks are saying it has to do with diesel particulate burn off or something to that nature. Again, I spend approximately 15 miles on highway daily to & from my office which means there are plenty of chances for burn off to occur without knowing it because the vehicle is cruising on the freeway.


I'd like to better understand what exactly is going on. From where is this "particulate" being burned off? Is it in the engine or exhaust system? Why is the fan running? Is it to blow the fumes or vapors out of the engine compartment or to cool something during the "burning" process. Thanks.


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## bayoucity (Jun 11, 2010)

rmorin49 said:


> I'd like to better understand what exactly is going on. From where is this "particulate" being burned off? Is it in the engine or exhaust system? Why is the fan running? Is it to blow the fumes or vapors out of the engine compartment or to cool something during the "burning" process. Thanks.


Attached is the design of the module. I will appreciate if any in-house diesel engineer will chip in & put everything in layman terms. (I think either bimmerdiesel or flyingman is a diesel engineer). The car is designed to cool off the module during & after the burn off.


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## rmorin49 (Jan 7, 2007)

bayoucity said:


> Attached is the design of the module. I will appreciate if any in-house diesel engineer will chip in & put everything in layman terms. (I think either bimmerdiesel or flyingman is a diesel engineer). The car is designed to cool off the module during & after the burn off.


Thanks, this is helpful and I look forward to our resident "diesel engineers" chiming in to explain it in non-engineer terms.


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## bayoucity (Jun 11, 2010)

*Location of the different units.*

My bad! I'm probably confusing you without providing a bigger picture. The diagram below show you the location of each unit. The module mentioned on the previous post is located on #13 as you can see it needs as much air intake from the front to cool off during the operation or incomplete burn off. Please correct me if I am wrong because this is how I understand it.


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## Flyingman (Sep 13, 2009)

It is a rather simple process. Unburned or incomplete burned fuel (hydrocarbons) particulates are captured by the filter screen which is later subjected to very high temperatures (ocassionally) to burn them off.

Just think of how your oven self cleans. All the grease and unburned particulates accumulate over time and then you deliberately raise the temp very high to oxidize or burn it off leaving only a very fine dust that is easily blown off.

Oven gets hot as hell! 

It is what we call PFM!:rofl:


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## rmorin49 (Jan 7, 2007)

Flyingman said:


> It is a rather simple process. Unburned or incomplete burned fuel (hydrocarbons) particulates are captured by the filter screen which is later subjected to very high temperatures (ocassionally) to burn them off.
> 
> Just think of how your oven self cleans. All the grease and unburned particulates accumulate over time and then you deliberately raise the temp very high to oxidize or burn it off leaving only a very fine dust that is easily blown off.
> 
> ...


Now I am beginning to understand why the 335d costs more than a similarly equipped 335i. I am also curious to know if our friends at the EPA include the emissions from this "burnoff" in their emissions calculations. What tells the car it is time to perform one of these "burnoffs". I doubt it is mileage as my car has only been driven about 800 miles, mostly highway at 60-75 mph. Both of the burnoffs were conducted after a much shorter, perhaps 2 mile in town drives at less than 40 mph.


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## dunderhi (Dec 10, 2006)

The burn-off is why your car doesn't spew a black cloud and why tail pipes look clean. I'm not a diesel engineer, but if you are having frequent burn-offs, I would try a different fuel station for your diesel or a maybe diesel fuel additive. I really don't notice burn-offs much anymore (BTW they only happen during light throttle use), but I would guess I only see them only once every three to five tanks (1350-2350 mi).


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## Flyingman (Sep 13, 2009)

I have not noticed one in a long time now. Used to give off a very peculiar sweet pungent smell, like "Napalm in the morning" kind of smell.:rofl:

As my commute involves a rather long stretch of hwy at high speed (80mph+), I don't really notice it.


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## wxmanCCM (Feb 17, 2010)

rmorin49 said:


> ...I am also curious to know if our friends at the EPA include the emissions from this "burnoff" in their emissions calculations....


Probably not, but I'm not really sure; I haven't seen anything specifically about DPF regeneration procedures in the regulations. The PM emissions are measured during the FTP75 test cycle ( http://www.dieselnet.com/standards/cycles/ftp75.html ) and have to be certified at the 120,000 miles useful life interval. The 335d has certified PM emissions of 0.000 g/mile, implying that the PM emissions are less than 0.0005 g/mile or 0.5 milligrams/mile.

Even during regeneration, studies have shown that PM emissions increase, but only to the level typical of modern gasoline cars. Most of the time, DPF-equipped diesel vehicles have PM emissions that are indistinguishable from background levels.


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## bayoucity (Jun 11, 2010)

rmorin49 said:


> Now I am beginning to understand why the 335d costs more than a similarly equipped 335i. I am also curious to know if our friends at the EPA include the emissions from this "burnoff" in their emissions calculations...


Ironically, EPA is the one that makes BMW place this expensive SCR on all the diesels.


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## János (Jun 19, 2010)

Flyingman said:


> I have not noticed one in a long time now. Used to give off a very peculiar sweet pungent smell, like "Napalm in the morning" kind of smell.:rofl:


I am reminded of burning caramel. :yumyum:

Somewhere on this forum I seem to recall someone saying that if you do a lot of in-town driving you would encounter the regen cycle more frequently, as the engine doesn't run as hot.

Don't know if that is true or not, but it sounds logical.


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## Penguin (Aug 31, 2003)

bayoucity said:


> Ironically, EPA is the one that makes BMW place this expensive SCR on all the diesels.


Your comment is correct about being an EPA requirement, but the particulate burn off has nothing to do with the SCR system, it is the DPF (Diesel Particulate Filter) system. The SCR system mainly reduces NOx emissions.


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