# Urea tank - question



## jkp1187 (Jul 2, 2008)

So I understand that the 335d won't allow itself to be started if the urea tank is empty. But what if you're in a location that doesn't lend itself to easy access to a refill of the tank. Can you just fill the tank with water until you have a chance to get the appropriate fluid?


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## d geek (Nov 26, 2008)

First off- several warnings are generated before you are completely out of DEF and the car is disabled, so no excuse to run it out completely.

Secondly- if you have received several warnings and want to push it to the limit, then purchase a bottle of DEF to have at the ready.

Third- water into the DEF reservoir? in a $45-60K vehicle with a very advanced emissions control system? are you serious?


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## jkp1187 (Jul 2, 2008)

d geek said:


> First off- several warnings are generated before you are completely out of DEF and the car is disabled, so no excuse to run it out completely.
> 
> Secondly- if you have received several warnings and want to push it to the limit, then purchase a bottle of DEF to have at the ready.
> 
> Third- water into the DEF reservoir? in a $45-60K vehicle with a very advanced emissions control system? are you serious?


Yes, I am serious. Do you have an answer for the question?


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## d geek (Nov 26, 2008)

yeah- here's your answer:

eff no


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## jkp1187 (Jul 2, 2008)

d geek said:


> yeah- here's your answer:
> 
> eff no


What is the basis for your conclusion?


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## d geek (Nov 26, 2008)

jkp1187 said:


> What is the basis for your conclusion?


because DEF is what the system uses :dunno:

what happens if something else is put in there? who knows? who would like to volunteer to find out? why would you want to when it would be so easy to avoid this "problem"? :dunno:


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## jkp1187 (Jul 2, 2008)

d geek said:


> because DEF is what the system uses :dunno:
> 
> what happens if something else is put in there? who knows? who would like to volunteer to find out? why would you want to when it would be so easy to avoid this "problem"? :dunno:


Because I like to know how cars work. Especially when they cost $45k - $60k. I'd hate to spend that much on one only to find out that this urea contraption left me stranded.

Can anyone who knows something about the engine and urea filter system help me with an answer to this question? Will using water in place of urea cause significant damage to the system? (Will it work at all?)


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## d geek (Nov 26, 2008)

here is a link to a presentation of the system that was eventually deployed:
http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2007/session4/deer07_mattes.pdf (SCR description starts on pg 16)

you're right- i cannot answer your question on a technical level. But the thought of putting the wrong fluid into such a complex system frightens me. i don't know why anyone would ever risk it on such an expensive vehicle, and that is what i was trying to express


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## Penguin (Aug 31, 2003)

jkp1187 said:


> So I understand that the 335d won't allow itself to be started if the urea tank is empty. But what if you're in a location that doesn't lend itself to easy access to a refill of the tank. Can you just fill the tank with water until you have a chance to get the appropriate fluid?


Well, your can try it and find out, but... I would be extremely surprised if the EPA would approve a system which could be defeated by simply using water instead of DEF, considering the fact that they required BMW to design the system to make the engine inoperative when the DEF fluid runs out. Being able to defeat that mandatory "feature" by simply filling the DEF tank with water would almost surely be an eventuality that the EPA would have considered and required an answer to. I suspect there is a sensor in the system that can tell the difference between DEF and plain water.

As the system uses "A nitric oxide sensor downstream of the SCR catalyst provides feedback on the concentration of NOX in the exhaust emissions," if nothing else use of water would probably ensure a SES light.

P.S. Mercedes does have a sensor in the DEF tank to tell if you have put water, rather than DEF, in the tank:

"Sensors in the tank detect the correct urea concentration. A separate NOx sensor monitors the exhaust. Filling up with water won't suffice."

http://www.autoweek.com/article/20081020/FREE/810199990

I would be extremely surprised, no, make that flabbergasted, if BMW did not have something similar.


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## Stugots (Jan 1, 2010)

Everything we know about Urea and the tank says there's a mixture that needs to be in the tank for it to work properly, and that is electronically managed, and released. Also, d geek is right. Putting water in that tank is akin to putting water in your gas tank. Not a very bloody intelligent thing to do.

If you ignore the 1000 miles of warnings the car gives you and you run out of urea, well...bad job you.


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## d geek (Nov 26, 2008)

there was a guy on this board who claimed he and his buddies pissed into his tank and it didn't seem to have any ill effects :tsk:

haven't seen him post in a few months though...


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## Kamdog (Apr 15, 2007)

d geek said:


> there was a guy on this board who claimed he and his buddies pissed into his tank and it didn't seem to have any ill effects :tsk:
> 
> haven't seen him post in a few months though...


Maybe he wasn't pissing in his own tank, and maybe he had no ill effects of that night of heavy drinking.


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## d geek (Nov 26, 2008)

Penguin said:


> ...P.S. Mercedes does have a sensor in the DEF tank to tell if you have put water, rather than DEF, in the tank:
> 
> "Sensors in the tank detect the correct urea concentration. A separate NOx sensor monitors the exhaust. Filling up with water won't suffice."
> 
> ...


from the 335d manual:



> Wrong fluid
> (icon shown here) A warning lamp lights up:
> The wrong fluid was filled into the reservoiir.
> 
> Please contact your BMW center.


and this interesting note:


> Wrong fluid
> (warning icon here) If you add the wrong fluid, e.g. antifreeze
> for washer fluid, do not start the engine;
> otherwise there is a danger of fire


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## Stugots (Jan 1, 2010)

d geek said:


> there was a guy on this board who claimed he and his buddies pissed into his tank and it didn't seem to have any ill effects :tsk:
> 
> haven't seen him post in a few months though...


With the appropriate amount of Nitrogen in your urine, that's entirely possible (but not really intelligent).


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## tlak77 (Aug 5, 2009)

why not put gasoline into diesel tank or vegetable oil instead of engine oil.....or just fill it all with water
DER is just another fluid you need to add/change to have your "d" operational.
OP if you are really concern about DEF you need to look into other vehicle, and not stress about it.


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## bcamp16 (Mar 18, 2010)

*Diesel Exhaust Fluid*

This Diesel Exhaust Fluid is getting way out of hand in my opinion.I am a sales rep for Superior Fuels and Transport in Fort Worth,Texas and we are distributors for DEF...It is manufactured by Terra Industries and has all the API ( American Petroleum Institute) certifications..If you want to fill the reservoirs yourself, one can go to any Freightliner, Peterbilt, Kenworth dealer and purchase the fluid...Or if you live in the Dallas/Ft.Worth area i will be glad to help you.
I haven't purchased a 335D yet but am just dying to do so.I have a friend who is an aircraft mechanic that has one and he just loves it and he just got his first DEF warning the other day.Please let me know if i can help in any way.
Apparently the X5D has been having all kinds of issues regarding the DEF freezing etc. Have you all seen this [email protected]:thumbup:


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## jkp1187 (Jul 2, 2008)

Penguin said:


> Well, your can try it and find out, but... I would be extremely surprised if the EPA would approve a system which could be defeated by simply using water instead of DEF, considering the fact that they required BMW to design the system to make the engine inoperative when the DEF fluid runs out. Being able to defeat that mandatory "feature" by simply filling the DEF tank with water would almost surely be an eventuality that the EPA would have considered and required an answer to. I suspect there is a sensor in the system that can tell the difference between DEF and plain water.
> 
> As the system uses "A nitric oxide sensor downstream of the SCR catalyst provides feedback on the concentration of NOX in the exhaust emissions," if nothing else use of water would probably ensure a SES light.
> 
> ...


Got it. Well, thank you very much for providing some useful information, Penguin! This thread sure generated a lot more chaff than was really necessary, though I suppose everyone loves the smell of their own flatulence at the end of the day....


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## jkp1187 (Jul 2, 2008)

tlak77 said:


> why not put gasoline into diesel tank


Because that may cause damage to your engine. The urea tank is not part of the *engine* to the best of my knowledge. Presumably, if you could find a way disable the sensors, there would be no mechanical problem with running the engine without the urea tank.

I suggest you check out howstuffworks.com -- there is a lot of good information explaining how engines work there.

I must confess, the fact that this tank seems to be so difficult to defeat -- and indeed that it has the ability to prevent the engine from starting if the sensors doesn't detect not just the right amount of fluid, but the fluid composition -- makes it less likely that I'll be interested in a BMW diesel at this time. Just one more thing to break.


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## d geek (Nov 26, 2008)

jkp1187 said:


> ...I must confess, the fact that this tank seems to be so difficult to defeat -- and indeed that it has the ability to prevent the engine from starting if the sensors doesn't detect not just the right amount of fluid, but the fluid composition -- *makes it less likely that I'll be interested in a BMW diesel at this time.* Just one more thing to break.


us future used BMW diesel owners thank you :thumbup:


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## Penguin (Aug 31, 2003)

jkp1187 said:


> Just one more thing to break.


Well, I won't get into a comprehensive reliability comparison of gasoline vs. diesel, but I would point out that while the SCR system is indeed "one more thing to break," on the other hand, the diesel has no ignition system, so that is six less coils to break, as well as the other components associated with providing a spark at the right time to the right cylinder.


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## tlak77 (Aug 5, 2009)

Snipe656 said:


> Strangely enough I bet when some of the other emissions equipment fails the car still drives yet would not be meeting compliance either.


That is always a probability Snipe..
OBD could fail as well in any car, I presume, and it could cause incorrect readings while having emissions checked.


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## Snipe656 (Oct 22, 2009)

I was thinking specifically when a cat goes bad. If the computer is anything like all the other cars I have had it will know via the pre and post O2 sensors that the cat has gone bad. Yet I bet anything the car will still drive, perhaps in some sort of limp mode but drive none the less.


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## tlak77 (Aug 5, 2009)

Snipe, agree limp mode would be nice "option", something what 335i does when HPFP fails or similar...


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## wxmanCCM (Feb 17, 2010)

tlak77 said:


> Snipe, agree limp mode would be nice "option", something what 335i does when HPFP fails or similar...


I agree. It's my understanding based on articles I've read that the 2010 emissions-compliant diesel pickup trucks (i.e., the 2011 Ford Powerstroke and the 2011 GM Duramax) go into "limp mode" if they run out of urea.

Diesel engines produce virtually no NOx at idle or very low power output anyway, so there's no reason from an emissions perspective not to have that "option".


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## Flyingman (Sep 13, 2009)

Urea is required to have the proper chemical reaction, i.e. mix with exhaust and appropriate temperature for the reaction to occur.

When your windshield washer light comes on, do you wait till it goes dry or do you go ahead and top it off next opportunity?

I think this started out as a stupid thread folks. Just add the Urea when it is required, and forget about it. I suppose if you are really stranded and want to add beer, water, piss, whatever, go for it. It is no different than a flat tire and no spare. Only it will be much harder to find DEF in the middle of the night.

If I were doing a long trip I'd consider taking an extra bottle along for the ride, perhaps. Especially if I knew I'd be coming close to the limit for a refill. In fact, the prudent thing would be to top it off before your long trip, just like I would top off my winshield washer fluid, oil and brake fluid.


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## Snipe656 (Oct 22, 2009)

They should have put the filler for this up by the fuel neck, like the picture someone posted of I think it was a Ford truck. I have read there is eventually plans to have pumps with this stuff. Would be nice if you could just top off the tank every so often but of course that seems to go against the BMW method where they want to drain it all out and then fill it up and guess because of the shelf life this stuff has.


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## Tedj101 (Nov 24, 2009)

jkp1187 said:


> What is the basis for your conclusion?


BMW has a sensor built in to check to see if the fluid has the appropriate specific gravity. If it doesn't, the car won't start. This avoids both filling with water or diluting with some fluid other than DEF.

<TED>


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## Flyingman (Sep 13, 2009)

Tedj101 said:


> BMW has a sensor built in to check to see if the fluid has the appropriate specific gravity. If it doesn't, the car won't start. This avoids both filling with water or diluting with some fluid other than DEF.
> 
> <TED>


Makes sense, water has a Specific Gravity of 1.0. The sensor is most likely nothing more than a hydrometer type float. Wonder what the SG of DEF is?:dunno:

Here is an interesting link about DEF: http://truthaboutscr.com/what-is-def.aspx

And everything you wanted to know but were afraid to ask: http://www.fleetguard.com/pdfs/product_lit/americas_brochures/MB10033.pdf

Sounds like we should be able to find DEF at most major truck stops, for those of you that just have to wait until you run out!

And here is the MSDS (Material Safety Data Sheet) where you can find the SG, which is 1.09 (i.e. heavier than water). http://www.cervantes-delgado.com/MSDS-DEF.pdf

And I found this website MWERK? with some interesting actual refill action fotos.http://forums.mwerks.com/zerothread?id=4519018


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## bayarea2007 (May 20, 2010)

any chemistry major here? NOx + H2O = ? 
I'm not chemistry major, but my guess the product would be NOx and H2O. Or, could it be N2, H2 and O2, in that case would we see an explosion?
I would not put water in there


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## bayarea2007 (May 20, 2010)

Looks like pure water would not be enough to reduce emission: it's used in the second stage. It doesn't imply putting in water will destroy the car though

DEF (Diesel Engine Fluid) is a 32.5% solution of Urea (NH2)2CO. When the urea solution is injected into the hot exhaust gas steam the water evaporates. The urea thermally decomposes to form ammonia and isocyanic acid.

(NH2)2CO -----> NH3 + HNCO

The Isocyanic acid hydrolyses to carbon dioxide and ammonia:

HNCO + H2O -----> CO2 + NH3

The overall reduction of NOx by urea is:

2(NH2)2CO + 4NO + O2 ------> 4N2 + 4H20 + 2CO2


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## anE934fun (May 10, 2008)

bayarea2007 said:


> any chemistry major here? NOx + H2O = ?
> I'm not chemistry major, but my guess the product would be NOx and H2O. Or, could it be N2, H2 and O2, in that case would we see an explosion?
> I would not put water in there


Pure urea has a chemical formula of (NH2)2CO. The 2s are subscripted. DEF is urea diluted with distilled water to achieve the required specific gravity. I am not sure what your question is about. :dunno:


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## digitaldav (Dec 3, 2010)

Actually my dealer just told me "In a pinch you can add water to the DEF tank, but you didn't here that from me". He left that message on my cell. I won't be doing this, I just couldn't believe he left that as a message on my cell.:dunno:

32.5% high purity urea and 67.5% deionized water this is the make-up of UREA.


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## EMC (Jan 22, 2006)

Alright...I let my DEF system run a bit low and got to around the 600 miles left before the "no start" condition.

I was out of town, so I called another dealer and they only had the 2.5 gallon containers of DEF fluid for $30...no small funnel with that container. The dealer said the only way DEF was covered under maintenance was if I had an oil change as well. I change my own oil more often than the service intervals, so it wasn't needed for another couple thousand miles.

I stopped at a Meijer gas station and grabbed a 1 gallon jug of DEF fluid for $6. Yes, $6. It even came with an accordion type funnel that screwed to the end of the 1 gallon jug. I refilled the DEF fluid and the warning went away after driving for 15 minutes or so.

DEF fluid is cheap. $6 and I'm still helping to keep the environment clean. ...No complaints here.


Also...for anyone in the Michigan area...all the Meijer gas stations now advertise their diesel as being Premium Diesel.


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## Stugots (Jan 1, 2010)

EMC said:


> Alright...I let my DEF system run a bit low and got to around the 600 miles left before the "no start" condition.
> 
> I was out of town, so I called another dealer and they only had the 2.5 gallon containers of DEF fluid for $30...no small funnel with that container. The dealer said the only way DEF was covered under maintenance was if I had an oil change as well. I change my own oil more often than the service intervals, so it wasn't needed for another couple thousand miles.
> 
> ...


Ask them what the actual Cetane level is, and then you'll know if it's really 'premium' or not.


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## EMC (Jan 22, 2006)

Stugots said:


> Ask them what the actual Cetane level is, and then you'll know if it's really 'premium' or not.


It's 50. Premium enough? 

It's been premium for a long time, but they are finally touting it as such. They have a little sign next to the pumps that states the benefits of premium diesel (up to 5% fuel economy increase, increased lubricity, etc.)


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## joeincs (Sep 15, 2009)

d geek said:


> from the 335d manual:
> 
> and this interesting note:


So this mornings Walmart ad has BlueDEF for sale for $11.50 for 2.5 gallons. At 48K miles on my D I am thinking about doing this refill myself when it calls for it. I know I saw it in this forum somewhere that it is not too hard to refill the tanks.


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