So where is the 2nd fill neck ?

Here is more definitive info on the size of the tanks. This was originally posted by Penguin in another thread.

"This is from the BMW Press Release:

AdBlue technology by BMW:

Optimized emissions without requiring additional maintenance.

To introduce AdBlue technology into the car, BMW has developed a two-tank system ensuring convenient use of this new technology with all the benefits and ease required by the customer. The amount of AdBlue required in each case is injected from the active tank (approximately 1.6 gallons in volume) by means of a dosage pump. And since the urea solution would freeze at a temperature of 12.2oF, this active tank, as well as the dosage pipes, are heated.

The active tank is connected to a second reservoir, referred to as the passive tank. With its additional capacity of approximately 4.5 gallons, this passive tank offers a plentiful supply of the urea solution. The average range provided with this supply capacity is indeed sufficient to have the tank system replenished only when the driver needs to change the engine oil. Hence, the large amount of AdBlue stored in the reservoir enables the customer to enjoy continuous driving, without having to change his/her service intervals. The driver therefore benefits from the advantages of this environmentally friendly emission technology throughout the entire running life of the car, without any additional service or visits to the workshop. Since all BMWs sold in the US benefit from The BMW Maintenance Program, the refilling of the AdBlue tanks will be a no-charge service for 4 years or 50,000 miles.

AdBlue from the active tank is delivered to the dosing valve and atomize into the exhaust system. Consistent distribution of AdBlue within the flow of exhaust is ensured by the SCR mixer. The ammonia generated in the hot exhaust flow subsequently acts as a reduction agent in the SCR catalyst and converts environmentally harmful nitric oxides into nitrogen and water vapor in a process referred to as a selective catalytic reaction (SCR). This process gives the special SCR catalyst its name.

The control of the SCR system is masterminded by BMW's powerful engine management computer. A nitric oxide sensor downstream of the SCR catalyst provides feedback on the concentration of NOX in the exhaust emissions.

Due to packaging limitations in certain vehicles, the position and location of the AdBlue tank may be varied from one vehicle model to the other. In the BMW 335d, the active and passive tank are at the rear end of the car, while in the BMW X5 xDrive35d, the active tank is housed in the front right section of the engine compartment, and the passive tank is under-floor next to the transmission."

So it appears that I remembered the tank sizes incorrectly. The total capacity is more like 6 gals, split between the small tank (1.6 gal) and the larger tank (4.5 gal).

I'm guessing it takes some fresh DEF to flush the system. So it would take more than 6.1 gals for a full service. This would explain the 6.5 gals on Craigs paper work. Or maybe they just rounded up to the nearest 1/2 gal.

Funf Dreisig

It's right beside the oil filter. It is partially obscured by the large black corrugated air tube. It looks just like the other one on the passenger's side of the engine.

Funf Dreisg

Here is a drawing of the X5 DEF system taken from a Feb 2007 slide presentation pdf. It may help people visualize just how complicated the DEF system is. Lots of tanks, hoses, pumps etc. There's a reason BMW hides most of this stuff under that pretty plastic engine cover with the logo.

Funf Dreisig

p.s. I'm not certain but I think Penguin originally posted the link to this pdf too.

I suspect that the PCD techs didn't know about the passive tank fill location, and only put as much DEF in the active tank fill when they prepped the vehicle..........

wow, i got the same message this morning, 994 miles left on my 2010 35d, great...

so, anybody tried refilling it themselves? DIY?

Diesel owners are alive again in this forum because seems like everybody is going down coz of this "virus"... lol....

OK here is some back of the envelope calculations about DEF volumes vs warning lights. WARING: this is based on fairly old documents gleaned via the internet. And they are probably worth almost as much as I paid for them :)

The only 'official' info on miles / gal of DEF that I've found was in the same pdf that included the 3D diagram of the system I posted earlier today. In part is says...

"Heating is limited to the UREA active-tank (pump, reversing valve, supply line) and the dosing line.

Heating only the active-tank enables constant energy input using available electric power.

Heating of the active-tank was chosen to consistently provide UREA by melting the frozen UREA in the active-tank in a reasonable timeframe.

As only the active-tank is heated, the passive-tank could be constantly frozen, if this occurs during a longer period, customer would have to refill the active tank, otherwise the warning system including the driver inducement would be activated.

Even at long periods below -11°C the heating concept consistently secures the UREA injection. The disadvantage is, that the customer could be forced to refill UREA in intervals of approx. 6.000 km.

Heating will start at temperatures below -11°C. There is no limitation to the operational range of the system. When the engine starts, heating will be activated."

The key part is the implication that when the passive tank is "constantly frozen", the active tank would still have enough DEF to drive 6,000 km or roughly 3,700 miles. Since the active tank is 1.6 gals (and in another part of this pdf it says that when the warning shuts down the X5 there is actually enough DEF for one more tank full of diesel) I rounded this down to 1.5 gals to drive 3,700 miles or roughly 2,500 miles / gal of DEF. As a reality check that would mean that when both DEF tanks were full there would be a range of roughly 15,000 miles. Which is not to far off a reasonable estimate of the miles / 'normal' oil change (ala BMW's CBS).

So if we assume this 2,500 mi/gal of DEF estimate is OK, the 1,000 miles to go DEF warning/gong should go off when there is only .6 gals of DEF left (i.e. 10%). IOW the 1,000 miles to go DEF warning/gong should go off when the passive tank is either completely empty (or frozen) AND the active tank is less than 1/2 full :yikes:

Funf Dreisig

Edit: Another reality check is included in the 2009 35d manual where it states on page 247 that the....
"Refilling quantity at the start of the reserve display: Approx. .75gal/2.7 Liter"
So this is in general agreement with the active tank being roughly 1/2 full when the 1,000 miles to go warning/gong goes off.

well, well, well,
now you guys have convinced me to stick with my 4,8 and appreciate it,
the last thing I want is additional technology, enough is enough
besides, here in our aera the cost of Diesel is always higher then the Super, and the X5 diesel has to be ordered with some package, so the hell with that, there is no economic justification, and I go to BMW service enou:dunno:gh already

best of luck, I will wait for the next Hybrid solution....

Is this a USA only system or will UK and European cars have it as well ?

It was designed to meet the California CARB emissions standards. It will eventually find its way to Europe....