BimmerFest BMW Forum banner
61 - 80 of 232 Posts

·
Registered
Joined
·
4,703 Posts
Hi Bananaman,
Yet again, you've found something that nobody else has reported (to my knowledge)!

Apparently, odors can get into the cabin if the engine-bay micro filters don't seal well!

I'll add checking the microfilter seals to the anti-stink DIY as yet another step in eliminating the stinky-poo AC!
Hello Blue.
Great work, you did here. This is the first time I see this post. I highlighted what I consider sensitive. Until last year every now and then I was experiencing some of that nasty smell, but I never got drilling the hole etc.
I also noticed that every time I went to the carwash, my front right side of the windshield would fog up with the HVAC on.
I bought a couple filters and went to change them. Here it gets interesting.
The 2 little draining tubes #5 circled, were plugged solid with leaves and dirt.
Then what BMW calls "microfilter air channel" and is #7 circled, on the passenger side was installed wrongly. It was not sealing properly, because it was not attached properly to the duct that goes inside the cabin - reason why my windshield was fogging up inside on the passenger side every time I was in the carwash (this whenever it was cold).
Once I cleaned the drainage tubes and sealed the air channel, and it's exactly one year now, I never had a "stinky" problem. However, i will check those 2 drainage tubes from under the car.
Thanks everybody for your contribution.

Auto part Diagram Automotive lighting Line art
 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #62 ·
I cleaned the drainage tubes and sealed the air channel ... i will check those 2 drainage tubes from under the car
I too must admit my microfilter drainage tubes were packed with leaves & clogged solid, similar to the pic below from this thread.

I must admit, my stink abated a LOT when I cleaned those micro filter tubes out with a coat hanger!

 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #63 ·
Here's a picture of my cabin filter drainage.

It's almost clogged again.

Time to clean it out to avoid the dreaded AC gym sock stink!

 

Attachments

·
Registered
Joined
·
4,703 Posts
Although BMW calls for a once a year deal - for changing the air cabin filters - after I unclogged the drainage tubes on my car, I actually open the 2 boxes every 2-3 months and clean them out. I also shake the filter elements of the crap they accumulate.
I can tell there is lots of dust besides those pesky dry leaves that cumulates in there.
As Donna showed in the previous thread, how quickly the dirt accumulates there in those 2 drainage tubes, you have all that crud on the bottom of those 2 plastic filter holders / boxes. My car has no smell for quite a while now.
 

·
Registered
Joined
·
897 Posts
Another interesting e39'ism and I thought that the short blast of rot was outside my car! I have the 5 seconds of what the #$ck is that smell when I turn on the AC, then nothing : ) I suspect it is due to the shut down / seal everything off action noted above. I did change my charcoal filters when I bought the car two months ago but did not check the drains. I did notice one of my old filters was upside down! I'll have to check tomorrow the drain hoses... otherwise coldest AC I have ever felt... lucky my stink is for 5 seconds I guess.
 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #67 ·
Check your undercarriage drain tubes (these will be hard to unclog)

In addition to unclogging both cabin-air filter drain tubes, make sure you check both undercarriage drain tubes for dripping water!

I crawled under the car today to check, since warm season is coming up.

Both undercarriage drain tubes were dripping water, which is a good sign.

Both foot-long tubes are very flexible so I felt for any debris inside; yet, as was previously noted, it's going to take ingenuity to figure out how to unclog these drain tubes because they make a 90° bend into the sheet metal of the floor.

Let's hope yours never clogs!

Here are some pictures. It's a bit hard to move the camera far enough away to get a good shot of both drain tubes; someone can get a better shot from a lift rather from the ground.

The question will be how to unclog them if they clog up?

 

Attachments

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #69 ·
Are those pics of the drain tubes with your underpanels on or off?
I didn't remove anything; I just drove up on ramps so that I would have room to slide under the car to look at the two air conditioning undercarriage drain tubes.

The AC undercarriage drain tubes are located just about along the length of the transmission, at least in the 2002 E39 they are.

 

·
Freude am Fahren
Joined
·
2,400 Posts
So just how is this debris going to get in these drain tubes? They only drain condensation from the AC evaporator coils. The air in the system has to go through the cabin filters to get there, so there shouldn't be any debris in the system. My drain tubes get flushed out every couple months when I pop open my access hole and treat the evaporator coils. It is kind of a pain, but now that I have the hole in there, and the tool made, it only takes about 15-20 min. once every few months to keep the stink away.
 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #71 · (Edited)
So just how is this debris going to get in these drain tubes?
Checking & clearing the drain tubes is just one of many approaches as listed in this post (#31) above. We still haven't 100% identified the culprit (it may have multiple culprits).

Another approach is to spray disinfectant up from the drain tube; but both these approaches have problems (as noted in post #31 already).

So, I agree. The cabin air filter drain tube is muuuuuch more likely to become clogged and to bring stink into the cabin.

Seems to me if these undercarriage train tubes are leaking condensate, then, probably, they're not clogged. Right?

 

·
Registered
Joined
·
897 Posts
I didn't remove anything; I just drove up on ramps so that I would have room to slide under the car to look at the two air conditioning undercarriage drain tubes.

The AC undercarriage drain tubes are located just about along the length of the transmission, at least in the 2002 E39 they are.

I'm not seeing any water come out of my drains (at least no puddles on the ground)... I'm going to check tomorrow after my 20 minute drive to work, looks like they are just after the rear end of the auto trans pan (can see a dirty green ATF sticker in the pic) near the cross member - drive shaft. I'm thinking of putting my air hose up to them and blowing up to clear things and then hope they drain... any danger in blowing 80 psi up into the system that anyone can think off... I figure it will dislodge anything and then hope it drains out the tube... might be wishful thinking.
 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #73 · (Edited)
Blowing air in the undercarriage AC drain hoses might unclog them!

I'm thinking of putting my air hose up to them and blowing up to clear things
Now THAT's the kind of novel idea we're in desperate need of here!

At least the air would go past the 90° elbow into the floorboards!

I'm guessing water would work also (a modified garden hose perhaps?) but it might make a mess inside so air might be better.

You are correct that the drain hoses end just aft of the transmission cross member. They start right about midway of the transmission, on each side of the transmission and then drain backward past the crossmember just in front of the drive shaft exiting the transmission.

The picture below might show that more clearly (the engine is to the right and the drive shaft is to the left in the photo below).

NOTE: Without a lift, I couldn't get far enough away to show BOTH AC floorboard drain tubes; if someone has a lift, they would be able to get a much better picture than I can on my back under the car.

 

·
Mach Schnell!
Joined
·
25 Posts
Source of debris

So just how is this debris going to get in these drain tubes? They only drain condensation from the AC evaporator coils.
From what I saw when I cleaned mine out the other day the material was a combination of particulate matter (pollen would be a good guess in here in the Old North State) and mineral build up. I have to assume that since this water is being sucked out of the air, there would be a certain amount of mineral content that would be left as residue from the evaporation process. Much like mineral content left after a pan of water is left outside.

Mine still spit water in the passenger floor board so since I have a extended warranty I decided to let the dealer have shot at it.
 

·
Registered
Joined
·
897 Posts
I'm going to experiment when I change the ATF fluid with different air pressures up the drains. I have a cone air attachment with a small handle to blow air so it should fit snug into the hose. I'm going to start with 40 psi as I dont want to blow the 90 degree fitting apart and then have to battle to get to it. I dont see any water dripping under mine so have not used the AC since I read this post, dont need a pond building up in my AC system!
 

·
Registered
Joined
·
342 Posts
... We still haven't 100% identified the culprit (it may have multiple culprits).
I am fairly convinced, at least in my case, that the stink is a result of funky stuff growing within the system after the car is shutoff. Based on what I have read, learned, and experienced so far, I think it is a system design flaw.

For my vehicle, my thought process is this:

1. Cabin air filters are brand new and the associated drains here are not clogged. There is no odor in this area when checking under the hood.

2. Water drips in two spots under the car when the AC is running, therefore these drain tubes would seem to be functioning properly as well.

3. Stink when starting the car seems to vary, probably with weather / humidity and trip frequency. I've not keep notes or anything, but I think when the car is parked for a very short time ( < 1/2 hr?) or a very long time (several days?) the smell is less noticable. Intuitively, I would think more humidity and a certain temperature range would be more conducive to the growth of the funky stuff (mold or bacteria?) that causes the smell. (Someone previously decribed this more scientifically, but I don't recall the exact details.)

My Conclusion: Something about the design of the system makes it inherently more likely to stay damp and grow more stink. Yes, the same phenomenon may occurs on many other makes and models, but something about this particular system makes it much worse. Assuming the drain tubes underneath are working, then either the housing that the tubes drain from is poorly shaped / sloped, or some combination of flaps and vents are improperly closed when the car is parked, hampering the natural evaporation of any remaining moisture in the system. (Or both?)

Regading the second part of the theory, I have seen comments about someone "wiring" some part of the system to stay open or partially open after the vehicle is shut off. Does anyone have any technical details on that?

I have read many solutions regarding changing your usage patterns, i.e. turning the compressor off 5 minutes from home, changing to recirc vs. outside air for less humidity, and even blasting the heater occaisionally to cook off the bacteria. I don't have to do these crazy things in my other two "cheaper" vehicles, so why should I have to with my new found "luxury" vehicle?

If anyone has any reasonable re-engineering ideas, I'm all ears.
 

·
Registered
Joined
·
897 Posts
I am fairly convinced, at least in my case, that the stink is a result of funky stuff growing within the system after the car is shutoff. Based on what I have read, learned, and experienced so far, I think it is a system design flaw.
My cabin filters are new also, drains up there clear / like new, drain from windshield to fender drains clear / like new.

I had the "stink" once, then nothing now which prompted me to search this forum for AC stink, but I'm going through the car like I have on my past two BMWs for EVERYTHING that can go wrong so I get 5-10 years of hassle free BMW'ing!

Interesting experience last week that could be related to all this... While I was under my car for an hour cleaning the transmission pan (pending pan drop / filter / ATF) and finding some peace, solace and satisfaction in turning black control arms into shining examples of aluminum fabrication I noticed the sound of a drop of water into a puddle with an echo to boot. I had my AC on just before pulling up on the ramps so all I can figure is that there is a nook in the system where a puddle of water can form and a drip of some sort falls far enough to make a "plop". It is too bad that there is not a good view of an assembled AC system, the break outs just dont show where everything fits together. My feeling is that even with flowing drains, the design has a water gathering spot and this is where the pond scum forms. Maybe when drains clog, your pond gets larger so stinks worse or maybe us northerners kill the pond every winter unlike southerners that use AC year round and feed your ponds on a regular basis. Funny thing is, my car is a FL car so either a) the previous owner never used AC (hence didn't notice clogged drains or wet feet) or b) the reason it only had 59,000 miles on it, is the owner never used the car!

With all the brain power on this problem from this thread, the question now is where in the system can a drop of water form, have enough vertical travel to make an impact noise that you can hear from under the car at the front edge of the tranny pan cover (I entered the underworld of my car from the front)?
 

·
Seek to understand,^Value
Joined
·
25,199 Posts
Discussion Starter · #80 · (Edited)
Next time somebody parts out their E39, they need to get some pics of the parts of the AC system that are deep down inside. Any volunteers? :eeps:
I agree the diagrams don't help all that much and one good picture of the guts of the AC vents south of the evaporator might pinpoint the stink.

Also, the wired vent has never been identified (I asked a year ago myself); so, it's either wrong information or we lost it.

As for what we can do, for now, there's only the recommendations left in post #31 above.

 
61 - 80 of 232 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top