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What can we modify on the E39 to drain dank AC evaporator pan pooled water?

191K views 231 replies 61 participants last post by  brc5 
#1 ·
What can we modify on the E39 to properly drain pooled AC evaporator pan water?

After reading many BMW AC evap-o-stink threads on Bimmerfest, I think the BMW AC stink problem is a BMW engineering problem that can be resolved with a Bimmerfest engineering fix.

Multiple "workarounds" have been proposed (I can summarize them for you later) but what I'm asking in this thread is for Bimmerfest suggestions to daily mechanically DRAIN the POOLED WATER that is the primary cause of this BMW A/C smell problem.

What part would you modify to drain the pooled water in the BMW E39 air conditioning evaporator water collection pan?

 

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#2 · (Edited)
Summary of the workarounds proposed for smelly BMW AC

Proposed workarounds:
1. Once a month, turn the heat up to 90 and let it blow for 15 minutes.
2. Each day, turn the AC off five miles before you arrive at your destination.
3. Set the AC to 72 degrees, "Auto", "Snowflake", & "Circle without the A"
4. Drill a hole near the gas pedal side panel & spray disinfectant monthly
5. Drill a larger hole & periodically clean the evaporator fins with a toothbrush
6. Unclog the drain hose for the AC condenser (under the center console)
7. Replace the "micro" filter once a year (or more if it seems wet in monthly tests)

Presumed rationale:
1 & 2 --> dries up the water the bacteria, mold, & yeast need to thrive
3 --> reputedly supplies less water (but some say this step is useless)
4 --> kills the bacteria & yeasty beasties that are thriving on excess condensate
5 --> removes oils and contaminants that allow moisture to collect & beasties to grow
6 --> reduces the amount of water available (if and only if the hose was clogged)
7 --> I don't see how replacing the micro filter will help at all (do you?)

Proposed engineering solution:
8 --> Modify the E39 evaporator collection pan system so that water no longer pools

Presumed rationale:
8 --> drain collected water so there is nothing for the beasties to thrive on

 

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#3 ·
What part would you modify to better drain the AC collection pan?

As one of the steps in engineering a mechanical fix to the stinky BMW ventilation system, let's state the presumed sequence of events which cascade to cause the musty cabin odor.

This blurb says a lot:
1. It's first & foremost a design problem (due to compactivity or leakage)
2. Then, it's secondarily a moisture problem (due to excess moisture)
2. And, as a tertiary result, it's an organismic problem (due to stuff to eat)

Rather than attack the tertiary problem (kill the microbes) or the secondary problem (blow off the excess moisture with a variety of workarounds), why not resolve the design problem (too much water is collecting) by draining the excess water in the collection pan?

To start:
Does anyone have a photograph of the evaporator water collection pan?
Do you have a photograph of the drainage tubes from that pan?
What mechanical modification would you suggest to increase drainage from that pan?


.
 

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#4 ·
This thread is different than the rest (it's looking for a permanent solution)

To reiterate, this thread is different (I think) than the rest of the BMW cabin stink threads in that I'm not asking for us to come up with yet another workaround .... (like drilling holes and periodically cleaning & spraying).

I'm asking if we can come up with a solution.

The solution, it appears to me, would involve DRAINING out the water during and after each use (just like every other luxury car does).

Can you help me arrive at a permanent mechanical solution by proposing what parts to add or modify (with pictures if possible) to increase water collection pan drainage in the BMW E39?

 

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#8 · (Edited)
A behavorial workaround isn't a solution to an engineering problem.



It will come back. It has to. If the same conditions exist. The only real solution is an engineering solution which allows you to go back to the proper use model (which is to use the A/C like it's supposed to be in a luxury car).

I think we're close to the solution though. What we need to do is identify which duct is trapping the condensate; and then how to modify that duct to not trap condensate.

The problem right now is identifying which duct is the problem duct and then, how to modify it so that it's no longer the problem.

I would think BMW would have thought of this though ... so ... let's ask.

Does anyone here have a friend who works at BMW who can ask which duct is the problem duct?
1) Water drain (left, right) 64118367963 & 64118367964 $5.52 each
2) Condensation-water outlet hose (left?, right?) 64118369505 & 64118369506 $9.82 each
3) Left, Right condensation-water outlet hose 64116904641 & 64116904642 $9.82 each

Note: I can't find the "evaporator pan" in any diagram (can you)?

 

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#6 ·
The problem may be the drainage 'duct' having a sharp bend

Over in the E60 "stinky A/C" thread, it is said that the real problem isn't the lack of drainage of the evaporator collection pan but a too-sharp "duct" which collects water inside of it.

QUESTION 1:
Does anyone know if an evaporator collection pan even exists?
(I can't find it in the realoem diagrams).

QUESTION 2:
Can anyone confirm the real design problem lies in the "duct" shape?

QUESTION 3:
If it's the duct curvature, which duct do we think is the problem duct?
 

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#7 ·
Bluebee: You need to get the
1Z Einszett Klima-Cleaner Air Conditioner Treatment. I bought mine from Autogeek. It comes with a long tube that you insert into the center vents. The tube will reach the evaporator. Empty the can and allow the foam to work from approx 1 hour. You will see the foam liquid drain from your evaporator drain tubes. If you don't your tubes are clogged and must be cleared. Then turn up your fan and blow out the remaining odor. This has worked brilliantly for me since August 08. I will use another can in the spring and everything should be great.
 
#10 ·
Bluebee: You need to get the
1Z Einszett Klima-Cleaner Air Conditioner Treatment.
Disinfectant won't work for all of us based on my research (see quote below) ...

[FONT=Verdana, Arial, Helvetica, sans-serif]"There have been many postings on the various forums about dealing with this problem. Most of them recommend spraying some form of disinfectant/deodorizer into the fresh air inlets downstream of the micro-filters. Some even recommend removing the ducts between the micro-filter boxes and the firewall to get a better shot into the evaporator housing. Unfortunately the blower obstructs direct access to the evaporator coil/housing and limits the effectiveness of this method. It does work quite well for some owners but for others, (depending on the climate and vehicle usage); it becomes an almost never-ending task.[/FONT]"

 

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#11 · (Edited)
Unless you reengineer your duct work, the only alternative is to clean out the evaporator.
I think there are three possible ways to approach the problem:

Most insane approach:
1. Change our habits (e.g., cook the yeastie beasties along with ourselves or turn off the A/C five minutes before arriving home, etc.) ... (remind me why I bought a luxury vehicle again please - was it so I could babysit the A/C system?)

Most sane approach:
2. Disinfect our vents (e.g., drill holes in the foot well or spray foam down the vents) ... (ummm... again remind me why I bought a luxury car - was it so I could have endless mundane maintenance tasks of a poorly designed A/C system?)

Most elegant approach:
3. Modify our ducts (e.g., once we figure out which duct is the culprit, we can begin to see how we might eliminate the condensate caught inside the sharp curves of that problem duct).

 

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#12 ·
QUOTE]Most elegant approach:
3. Modify our ducts (e.g., once we figure out which duct is the culprit, we can begin to see how we might eliminate the condensate caught inside the sharp curves of that problem duct).[/QUOTE]

Do you know that the sharp curves are the culprit? It seems like the problem is more systemic rather than just the "sharp curves".
 
#13 ·
Doesn't anyone have a friend at BMW who can look this up for us?

QUOTE]Do you know that the sharp curves are the culprit? It seems like the problem is more systemic rather than just the "sharp curves".
I only know what I read here and on the net (and that my local BMW dealer told me to my face it is perfectly normal for a BMW to stink.)

It seems we don't really know where the excess condensation lies.
However, I'm convinced BMW knows where the engineering problem lies.

But I can't find a single photograph of the evaporator drainage system.

Doesn't anyone here on Bimmerfest have a friend at BMW who can pinpoint for us the engineering problem (ducts? coils? pans?)?

 

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#14 ·
Interesting!

My 98 528i runs fine, AC drains water dripping down the draintube to the driveway without problems.
I'd think if you get a stiff wire and crawl underneath to make sure the AC drain is not clogged and that should be sufficient.
I always turn OFF the AC 2 minutes before getting home.
 
#15 · (Edited)
Where is a picture of the drains under the E39?

get a stiff wire and make sure the AC drain is not clogged and that should be sufficient. I always turn OFF the AC 2 minutes before getting home.
It's a terrible suggestion to manually control the A/C so that it won't stink ... however ... there's nothing wrong with cleaning a clogged drain ...

This weekend, I'll lift the car and crawl under to find those drain hoses.

Since I'm decidedly not mechanically inclined, it would help if someone has a picture of the BMW E39 drain hoses under the car (I don't even know where to look).

Does anyone actually know what the AC evaporator condensation collection system really looks like?

 

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#17 ·
Finding the A/C drain under the car

I ran my a/c for the first time in a month and after 20 minutes I noticed my drivers side footwell front and rear was soaked. I think my drain is clogged.

I saw the photo and I will be looking for the drain near the transmission. If it is clogged what is the best way to clear it?

Should I blow compressed air up? Should I look for something with suction to suck the problem out?
What is the proper method?

Thanks
 
#18 ·
I think the real problem is when you shut the car off the air ducts close and with the cabin filters on top, you seal in all the air and moisture. A fellow BMWCCA member who lives in Sierra Vista, AZ (we use a lot of AC here in AZ) says he has permanently licked the problem. He wired the damper in the duct part way open, so it will never fully close. He claims it works flawlessly. I haven't got around to getting in there, so I continue to spray mine through the hole I made next to my gas pedal, every month or so.
 
#19 ·
I recently bought a used E46 that has the "stink" problem. I had the evaporator treated twice, and this improved the situation, but the car has given myself and two others asthma even after the treatment. I agree that a permanent fix is needed, not just a workaround. How did you wire the damper in the duct to stay open? Has anyone found out any further info about how to permanently fix the problem? Does your evaporator look normal when you have the "stink" problem? Would there be any obvious signs of mold? I took the car to an independent BMW shop and they found that the evaporator looked clean.

Thanks for your help.

Paul
 
#20 · (Edited)
Has anyone found out any further info about how to permanently fix the problem?
With summer coming up, it's time to resurrect this thread seeking a more permanent solution to eliminating the pooled water where the germs grow, causing the nasty AC stink.

Here are some cross references, but, all just propose workarounds:
My Car Stinks... Literarly!
Stinky AC
weird smell with heat on?
The return of Stinky AC
Nasty smell is hard to get out of the car
etc.

The closest permanent answer is to 'wire the duct open" .... but where (how?)???

What we need is a permanent solution. Does anyone have an idea on how to permanently eliminate the water from pooling in the too-small A/C evaporator ductwork?

 
#21 ·
I don't have the problem. My car is a 2002 525i. Carfax showed that it's been registered in Hawaii its whole life. One can assume the AC has been used year round for 7 plus years and the heater more than likely never used (OK, never say never, but at most maybe a few times). I do notice that the AC drains very well when it's parked and the AC is running.

I'm posting this to help, really. Did BMW redesign something in later E39s? Not having the problem, I really haven't read up on this subject to know if it affects "facelifted" E39s.

Here's hoping mine doesn't develop the problem. That would not be good, especially in Hawaii!
 
#22 ·
I don't have the problem. My car is a 2002 525i.
Mine is a 2002 525i also. And boy oh boy, does it have that dank stank!

I've learned the 'tricks' to avoid the stink but that doesn't mean I enjoy it.

- I've run the heater, in the height of summer, for fifteen minutes (presumably that cooks the bacteria, mold, and fungi and boils off the pooled water)
- I've sprayed disinfectant in the ductwork and onto the cooling fins of the evaporator
- I've replaced the air filters numerous times
- I've turned off the A/C ten miles from home to let it dry out a bit

I never did find the hoses that might be clogged so I've still gotta do that though!

And, I've never located how/what to wire to keep the ductwork open.
 
#26 ·
There are actually two drain hoses: one on each side of the trans.

I guess I'm the Lucky One here. We have very low-humidity summers here, so I get very little condensate dripping out. When I do smell something, I pull the cabin filters, and, with the blower on low, not recirc, I hose down the intake ducts from under the hood with Lysol spray, and let it set overnight.

I suspect the real problem is that the mould grows on the evap, which is moist from the A/C operation. That's why the foam stuff does the job, since it is able to penetrate the fins.
 
#27 ·
No A/C stink anymore! Change the cabin air filters and make sure they are not the cheapies, but the charcoal activated kind. I have has the car 3 years, and have changed the cabin air filters 4 or 5 times, because initially it smelled. No smell now at all, so I will just get on a yearly routine with those. I do sprinkle in a little baking soda as well on to the filters. Another thing, make sure that your cabin air filters are dry. If they are not installed correctly and the covers not attached, rain water can seep in and make them damp. As they say, "ask me how I know......" Keep the small rubber drain hoses clear of leaves and debris --these are located to the bottom of each plastic filter housing. I use a plastic straw to clean them out. It's flexible and something I had around the house. Run the A/C in the winter to keep it lubed up . I use it not only for cooling, but to get rid of moisture even in cold weather. I do let fan run after I turn A/C off--but not for 10 minutes, and not every time. I dunno, maybe because I use the heat during the winter, that somehow dries out whatever causes the damp smell? All I know is that the CC in this car is fantastic for the most part. I really like the fact that I can fine tune the dash vents using the center dial--seems like a small feature until you freeze/bake your face off in another car! Oh yeah, I also replaced FSU/FSR last Spring. Best of luck resolving this stinky problem.
 
#28 ·
No A/C stink anymore! Change the cabin air filters
Can you show me in a picture WHERE these "cabin air filters" are?

The only filters I know of are the two that are in the engine compartment along the bottom two corners of the windshield. Are you talking about those filters? (They don't seem to have carbon in them???)

Keep the small rubber drain hoses clear of leaves and debris --these are located to the bottom of each plastic filter housing.
Again, can you show me what you mean by these drain hoses?

Do you mean the drain hoses that people say come out of the BOTTOM of the car (meaning we have to lift the car to see them)?
 
#31 · (Edited)
With the summer in full swing, the AC stink problem arises again.

With another year under our belts, is this the recommended set of ac-stink problem statements and recommended solutions?

STINKY AC PROBLEM:
- It's first, and foremost, a BMW A/C downsize design problem (too cramped for proper ventilation of evaporator coils)
- The design problem allows food (dust), water (evaporator coils & ducts) and microbes (stinky poo) to coexist
- Resolution entails design, maintenance, & behavioral modifications (reduce the water, food, and stinky microbes)

DESIGN MODIFICATIONS: (Note: These are draconian)
- Cut hole in driver right-foot panel so you can spray germicide directly on evaporator coils (kill the stinky microbes)
- Drill a larger hole &
clean the evaporator fins with a toothbrush (less food for the stinky microbes)
-
Unkink the E39 evaporator duct (behind dash) by wiring the damper (less water for the stinky microbes)

MAINTENANCE MODIFICATIONS: (Note: These are judicious)
0. Reseat the two cabin-air micro-filters in the engine bay (BMW says stink can get in if they're not seated well)
1. Check if there is water normally draining from under the car after running your AC on a hot day
If there's no water pooling on both sides of your parking spot ... then ...
2. Clear the two undercarriage drain tubes any way you can:
- Some people suggest you snake a coat hanger past the multiple elbows to the evaporator coils to unclog
- Probably more reliable is to attach 13.5mm to 14.0mm OD plastic tube to both drain hoses & blow out obstructions
3. Unclog the drain holes & tubes in the two engine bay micro filters
- Some suggest snaking a six-inch length of coat hanger into the holes from the cabin filter downward thru the rubber drain hose
And, for more serious cases of BMW stinky AC:
4. Replace both engine-bay cabin "micro" filters (less food for the stinky microbes)
If eliminating water has been done, yet the stinky-AC microbes are still active ...
5. Spray tons of disinfectant in the air intake or directly onto the evaporator (through the drilled hole method).
- You'll need tons of germicide because it's not a direct shot to the evaporator coils from the air intakes
- Or try somehow to spray germicide upward hopefully onto evaporator coils from the undercarriage drain tubes
- While you're at it, spray ample germicide in central cabin vents (hoping some germicide lands on evaporator coils)

Note: The undercarriage drain tubes are apparently hard to remove for direct access to the evaporator coils; and, worse yet, they have a 90-degree elbow and 1-foot horizontal run, so, they're difficult to get a coat hanger into and even more difficult to get germicide up far enough to coat the evaporator coils.

BEHAVIORAL MODIFICATIONS: (Note: The fact we have to do this is ludicrous)
- Each trip, turn the AC off five miles before you arrive at your destination (less water for the stinky microbes)
- Park slightly nose upslope presumably so horizontal drain tubes drain better (less water for stinky microbes)
- Once a day, turn the heat up to 90 degrees and cook for 15 minutes (kill the stinky microbes)
- Set the AC to 72 degrees, "Auto", "Snowflake", & "
Circle without the A" (basic setup but doesn't help much)

Note: Yes, it's crazy to own a "luxury BMW" and then have to babysit the AC by turning it off or turning the heat up to 90 degrees in the hot summer so that it doesn't embarrass you with AC stink when you have a customer in the car; but, what else can you do?

 

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#32 ·
Drove my car a few weeks ago; really needs some a/c disinfectant :(

Thanks for the procedure, bluebee. I'm not f'ing turning off the air every time I stop the car :p but the other stuff will happen, if slowly***8230;
 
#33 ·
Great! All this talk about stinky A/C systems and now I'm starting to smell some funk in mine. Thanks guys! Got me all paranoid so I'll be doing a complete check this weekend.
 
#35 ·
I have a smell when the car initially is started with a/c running, but it rapidly goes away, so I am not too bothered by the problem. However, it's clear that some are greatly troubled. So, I just took a look at mine, partly out of interest. Here's what I found and suggest:

1. The drain tubes run on either side of the transmission (on my auto), towards the rear of the car. They actually run approximately horizontally for about 12" before the end of the tube is gound. On my car, the tubes actually end beyond the rear of the transmission and rest on top of a cross-member of some sort. That's probably why they are difficult to spot. I tried taking pictures, but the're not good pictures.

2. At great risk to health, I decided to see if they were blocked. Rather than poke a rubber pipe with wire etc, I stuffed a plastic tube about 1 inch up the drain, so it sealed nicely. If you try this, it needs to be 13.5mm - 14.0mm OD tube. That fits OK. I then blew down the tube.

3. On the LHS, there was a bubbly gurgling sound, like air bubbling through water and the end of the drain was wet also. On the RHS, the drain appeared dry and there was no bubbling sound, just air flow. Both tubes appeared unobstructed overall. You can actually hear all this inside the car if you get a long anough tube. My doctor assures me that Legionalla clears up quickly and not to worry.:yikes:

4. Observation: If, like me you park nose down on a slope in your driveway etc, then at the end of a journey, there will be water trapped at the elbow of the horizontal drain, unable to drain away. This could be one source of water accumulation and smell.

5. Suggestion: I assume these drains vent direrctly into the evaporator assembly. So, instead of drilling holes etc, why not shove the disinfectant spray directly up the drain holes from underneath the car? Once you know where they are, they are very easy to access, without lifting the car
 
#38 ·
Stinky AC DIY solutions (adding to the list)

I stuffed a plastic tube about 1 inch up the drain ... I then blew down the tube
Excellent tools/procedure to add to the stinky-AC DIY!

On the LHS, there was a bubbly gurgling sound, like air bubbling through water and the end of the drain was wet
Interesting observation. Would be interested to see if, say, after a week after you blew the LHS drain out, if the water returned or if the stink went away.

Legionalla clears up quickly
OMG. Legionella pneumophila lives in AC water and invades the lung! I hope you never sucked it in!

water trapped at the elbow of the horizontal drain
Another interesting potential solution; park the E39 nose up! (I'll add this to the list of potential stinky AC DIY solutions)

why not shove the disinfectant spray directly up the drain holes from underneath the car?
Yet another new and interesting potential stinky AC DIY solution! The whole problem with spraying the vents with germicide is that the microbes are reputed to live in the evaporator coils so very little (if any) germicide actually lands where you need it on the evaporator coils.

Access to the evaporator coils is the reason for cutting the hole but, as you note, cutting the hole is a pain so most people probably don't go to the effort.

However, if we can access the evaporator coils from the drain tube, then that might be effective. But I'm confused 'cuz you said the drain tubes had a one-foot horizontal path so I think you are suggesting temporary removal of the rubber drain tube (right?).

Is this the suggested procedure:

a) Lie down under the car and reach under to locate the 2 drain tubes
b) Remove the two drain tubes from under the car (probably by pulling off?)
c) Spray germicide directly directly up into the opening left by removal of the drain tubes (so that you can spray the evaporator coil and collection pan directly)
d) Blow throught each drain tube to ensure they are not clogged
e) Return the two drain tubes (presumably by pushing back into place)
 
#36 ·
And another thing.....

In the original post, I reckon part No 5 is the horizontal drain that runs under the car. part No 17 is the hidden pipe that runs vertically to connect to No 5 and this one is hidden from view, inside the car, and runs directly from the evaporator. Correct?

Also, the drain pipe under the car is cunningly bolted in place, so it cannot be easily moved.
 
#37 ·
BMW is too arrogant to believe their duct work is faulty.
I would believe that, my 1983 E28 533i had the same problem. It had a A/C system that was not automatic so I shut it off a mile or two before getting home. It helped. I also Lysoled the ducts but that was only temporary.

On the 2002 E39 540i, the stink is not consistant. Sometimes it does and sometimes not. I would love a solid fix for this issue. The area of the car that houses the A/C system is packed tight and wonder if the fix would be reasonable to attempt even if you could figure out that the moisture is pooling. Could it somply be hanging on the evaporator coils?

Keep us posted!
 
#39 ·
Would be interesting to know why some of us have this problem and others don't. For those who have the problem: Do you always have your air control on recirculate? My nephew did that and his truck always smelled like a cave. I tried to get him to put it on the fresh air setting but he was convinced that it (heating or cooling the air from outside) would hurt his gas mileage and performance
 
#41 · (Edited)
For those who have the problem: Do you always have your air control on recirculate?
Often, seemingly always when I have a customer in my E39, embarrassingly the AC stinks like an adolescent's gym socks!

My settings are basically permanently set at:
- Driver Temperature = 72 degrees
- Passenger Temperature = 72 degrees
- Vent control = Auto
- AC setting = Snowflake (always on)
- Recirculate =
Green light on the circle without the A
- Main spin dial = 3 bars blue (but not all the way so as to prevent "burp")
- Cockpit vents = all set to 1 (full on)

As far as I know, these are the standard recommended settings that I'm using - and I still have essence of gym sock oozing out of my AC.


But I too would like to know the answer to this question posed today by bananaman:
In the original post, I reckon part No 5 is the horizontal drain that runs under the car. part No 17 is the hidden pipe that runs vertically to connect to No 5 and this one is hidden from view, inside the car, and runs directly from the evaporator. Correct?


 
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