X5 35d - Exhaust fluid

[MINIz guy]

The vehicle is still at the dealership right now. Yes, you are correct with the mileage intervals too.

I don't believe that the dealership added any DEF fluid the first time, as nothing was stated on the service invoice. I posted exactly what the invoice said about the exhaust fluid issue. I will report again once we get our vehicle back.

[FunfDreisig]

Originally Posted by wch X5

My X5d also called for DEF at 900 miles. Dealer had me stop in and they found exactly what MINIz Guy's dealer found (100% in main tank, 66% in passive tank). The temperature was 35F outside....

I believe you. But this info simply does not make sense for a properly filled 35d DEF system....

We now have reports of two 35Ds to have their DEF warning trigger a 900 miles. In both cases the dealer reported the active tank @ 100% and the passive tank @ 66%.

AFAIK the DEF system holds a total of 6.5 gal: 2 gal in the main (active) tank and 4.5 gal in the passive tank.

So that would imply that these two 35Ds consumed 1/3 of the DEF in their passive tank in only 900 miles. 1/3 of 4.5gal = 1.5 gal IOW a DEF usage rate of 600 miles / gal of DEF => a full DEF system would only last 3,900 miles.

And yet we also have several reports of 35Ds that went 12,000ish miles without DEF issues.

Funf Dreisig

[wch X5]

I asked them about that. They showed me the print out from BMW computer that tells the techs step by step what to do. They entered in the values I stated above and the program that they were using indicated that this was normal.

I think they were as puzzled by this as all of us. Since they didn't want me to get stranded, they gave me a bottle of the fluid just in case.

I'm hoping that I don't get another one in 900 miles. I suspect that with time there will be some SIB about this.

[Craig]

I drove mine for a year 4850 miles and never saw a low DEF message. It looks like some of vehicles are using more than others?

Craig

[JCL]

Originally Posted by mandkole

I'm still wondering why the tanks require flush.... is it the underhood heat exposure of the active tank?

It is heat or cold that affects the shelf life of the fluid. In the automotive world, the emission controls regulations are more strict than in the heavy truck world. There was a lot of paranoia before SCR was introduced to this consumer market as to whether owners would bypass the urea systems, defeat them, etc. Old (stale) fluid won't necessarily hurt the engine, but the engine may not meet the emissions regulations. To satisfy the regulators, manufacturers agreed to put lockouts on the systems, ensuring that the urea system would function for the 100,000 mile limits mandated by the regulators. The flush procedure is driven by that concern. The fluid itself has a published shelf life of at least one year, if the temperature is kept within certain max/min limits. For that reason, bulk dispensors have climate controls built into the tanks. A vehicle like an X5 will see a wide range of environmental conditions during a year, so it is just to be safe. Some charts show fluid life up to 3 years. As more is learned (and real-world experience is gained) the one year rule may be relaxed at some point. Just my opinion on that last count.

[JCL]

Originally Posted by FunfDreisig

The area near the DEF filler fittings on our 35d has a very small amount of white crusty residue. I think this is dried DEF 'fumes'. I suspect the 'flush and fill' procedure is to make sure this residue does not build up in the various tubes and fittings. But .

Crystalization is described as normal on external components (ie where it is filled) but not normal on internal components. It occurs through migration by capillary action, according to the DEF industry.

Flushing and filling is to ensure that the fluid is effective in reducing emissions in the tailpipe, so that the vehicle continues to meet the emissions regulations.

[santo]

Is anyone concerned about extra moisture in the exhaust system introduced by the DEF system? Is the exhaust system 'beefier' so that it won't rust faster? I'm just a little worried tHat replacing the system cat to back is going to be astronomical in price and perhaps a BMW service center only item because of the cost of the components.

[Penguin]

Originally Posted by santo

Is anyone concerned about extra moisture in the exhaust system introduced by the DEF system? Is the exhaust system 'beefier' so that it won't rust faster? I'm just a little worried tHat replacing the system cat to back is going to be astronomical in price and perhaps a BMW service center only item because of the cost of the components.

You alreadu have moisture in the exhaust system, since one of the byproducts of combustion is water (you can see it dripping out of the exhaust pipes under the right conditions). I cannot imagine the little bit of moisture added by the DEF will make any difference, particularly since it will be a vapor in an exhaust of normal temperature.

[FunfDreisig]

Originally Posted by JCL

Crystalization is described as normal on external components (ie where it is filled) but not normal on internal components. It occurs through migration by capillary action, according to the DEF industry.

Flushing and filling is to ensure that the fluid is effective in reducing emissions in the tailpipe, so that the vehicle continues to meet the emissions regulations.

Thanks for the clarification. So simply draining and refilling with fresh fluid would meet that constraint.

BUT it appears BMW located both DEF tanks is not-so-handy locations for simply draining them. Perhaps that is why Craig got to witness a messy flush-n-fill machine in action

Funf Dreisig

[JCL]

Originally Posted by FunfDreisig

Thanks for the clarification. So simply draining and refilling with fresh fluid would meet that constraint.

BUT it appears BMW located both DEF tanks is not-so-handy locations for simply draining them. Perhaps that is why Craig got to witness a messy flush-n-fill machine in action

Funf Dreisig

I believe you are right. I also think that all those of you who volunteered to be early adopters should get gold stars, or at least sympathy cards.

I wanted a 535, but waited until they had built them for a year before ordering. The problem with the diesel is that it isn't just a new model, it has some technology (like DEF) that is brand new to BMW, and engine technology (diesel cycle) that is new to almost all of the BMW North American dealer technicians. Not difficult to understand, just different than the engines with ignition systems that they are accustomed to.

Add to that the uncertain outlook for diesel engines in North America going forward, and it may take awhile for diesels to become commonplace. Chrysler, Ford, GM, Toyota, Honda, have all pulled back on their diesel engine programs according to the reports. That is really leaving it to the Germans (BMW, Audi, Mercedes, VW) and likely Mazda to convince North American consumers that diesels are now mainstream. I am not sure this thread will help that cause....