[Yozh]

There is no Magic in filling those. Just do it slowly. I usually do the bottom/active first and then top one/passive.

[yellowjacket]

Hello Guys, I am a very NEW owner of a 2011 335D and so far (2 weeks) I love the car. I came from a VW Jetta TDI which was a great little bullet but not in the league of this animal. I did not need to use DEF in the Jetta so this is really new for me. I am very confused with all the discussion about filling a tank. Some say top some say bottom. My question is, If the top (passive) tank is the larger one that feeds the lower (active) one, why fill the lower tank? It seems that if you keep the top tank filled that it will pump the lower tank full as needed. Very confused.

[floydarogers]

Originally Posted by yellowjacket

.... I am very confused with all the discussion about filling a tank. Some say top some say bottom. My question is, If the top (passive) tank is the larger one that feeds the lower (active) one, why fill the lower tank? It seems that if you keep the top tank filled that it will pump the lower tank full as needed. Very confused.

The two tanks hold 3-5 gallons altogether. But the warning (999 miles til no-start) doesn't come on when the passive is empty; it comes on when there is only enough (given current usage) for 999 miles left. The active tank could be half empty.

Only way to get full range is to fill both.

[dixy2k]

Originally Posted by Schumacher62

like a few others here, i am able to fill the bottom port with no issues. but the top port wont take any def fluid.

as someone said, perhaps this is normal. but as someone else here said, they put quite a bit of fluid in the upper port with no difficulties.

i wonder, does the bottom cap need to be off when filling the upper port, to relieve any sort of vacuum preventing the upper tank from being filled? an acquaintance here in san jose has been extremely helpful with my fluid refill, and perhaps he or others here can come up with a definitive refill guide for the 335d. i dont believe its a blocked upper port: there was no crystalization present when i went to fill my upper or lower port.

has anyone developed a sure fire guide to refilling the def tanks?

thanks!

The air in the tank is displaced by the fluid going inside and it comes out through the neck of the bottle (if you are using the correct bottle to fill up the tank). Therefore there is no pressure build up which would prevent you from filling the tank.

[Yozh]

Originally Posted by dixy2k

The air in the tank is displaced by the fluid going inside and it comes out through the neck of the bottle (if you are using the correct bottle to fill up the tank). Therefore there is no pressure build up which would prevent you from filling the tank.

There are vents on both of the tanks, so you do not have to worry about the pressure build-up.

[yellowjacket]

Nice diagram but if you go by the manual and only put fluid in the bottom hole, how does the top passive tank ever get filled?

[Yozh]

Originally Posted by yellowjacket

Nice diagram but if you go by the manual and only put fluid in the bottom hole, how does the top passive tank ever get filled?

I do not have a manual, but perhaps it is designed as instructions for owners to top-up urea and then run to your dealer for a proper fill. As such, for a top-up, you would do it in the active tank/bottom tank/lower fill neck. However, as an owner, nothing prevents you to fill both tanks up to the max and enjoy the savings your friendly dealer would be happy to take away from you and charge you an additional $200 just to fill up your urea.

[yellowjacket]

OK
I think I understand. So I can fill the top (passive) tank just as I fill the bottom (active) tank. Does the top tank just take it from the bottle until it has enough and then I stop filling?

[Yozh]

Pretty much. Just go slow or you shall spill.

[dixy2k]

I actually squeezed the bottle to get more fluid in and I made no mess anywhere.
The bottle I used (bought from a VW dealer) has a screw on top, which makes it ease to refill.

[yellowjacket]

Wow, what a headache compared to my 02 Dodge Ram diesel with NO DEF. Will the 2 1/2 gallon jugs of blue from Auto Zone work in my 335d or will I need to buy BMW or VW ??

[montr]

Originally Posted by yellowjacket

Wow, what a headache compared to my 02 Dodge Ram diesel with NO DEF. Will the 2 1/2 gallon jugs of blue from Auto Zone work in my 335d or will I need to buy BMW or VW ??

I buy the 2 1/2 gallon to refill mine. I buy a 2.5 gallons at the nearest autopart store or Walmart. I have siphon from Harbor Freight and an adapter to a smaller tube from Lowes for an easy refill. When I tried to refill with the bigger hose of the siphon, it was too fast and overflow. This refill method is perfect, it take less than 5 mins. After refilling I just clean the siphon with clear water. Because the DEF fluid has a shelf life of about 1 year, I do not buy ahead. Also, I do not fill to the top. I only add 1 container of 2.5 gals when the car tell me it is ready to refilled. This way, I never have to worry about overflow or the DEF getting bad.

[floydarogers]

Originally Posted by yellowjacket

Wow, what a headache compared to my 02 Dodge Ram diesel with NO DEF. Will the 2 1/2 gallon jugs of blue from Auto Zone work in my 335d or will I need to buy BMW or VW ??

AFAIK, all the DEF is the same.

BTW, if you bought a newer Dodge (after '07?), you'd probably have to add DEF, too.

[yellowjacket]

YES I know that all new diesels use it thanks to our clean federal government. In fact my 2013 Jetta TDI did not use it but that is probably the only newer diesel that doesn't. What a great little car that was (48MPG). By the way, when your car tells you it is ready, which hole gets the 2 1/2 gallons that you talk about?

[dubulup]

went to the Vdub store yesterday...$32 for a .5gal bottle (that screws on) and 2x 2.5gal; 15min of my time...refilling the .5gal bottle. System full-ish.

can't imagine what my stealership would have charged.

[floydarogers]

Originally Posted by yellowjacket

...What a great little car that was (48MPG). By the way, when your car tells you it is ready, which hole gets the 2 1/2 gallons that you talk about?

Top is passive, bottom is active. Fill active first, then passive.

There are a few threads that show how to use the 2L VW container as an intermediate container so you don't get DEF slopped on the car and floor.

[Quasimodem]

Originally Posted by montr

I buy the 2 1/2 gallon to refill mine. I buy a 2.5 gallons at the nearest autopart store or Walmart. I have siphon from Harbor Freight and an adapter to a smaller tube from Lowes for an easy refill. When I tried to refill with the bigger hose of the siphon, it was too fast and overflow. This refill method is perfect, it take less than 5 mins. After refilling I just clean the siphon with clear water. Because the DEF fluid has a shelf life of about 1 year, I do not buy ahead. Also, I do not fill to the top. I only add 1 container of 2.5 gals when the car tell me it is ready to refilled. This way, I never have to worry about overflow or the DEF getting bad.

Another DEFusion. This is a common question, there are a number of threads on it.

It would be nice if somebody could consolidate the discussions and make a DEF Refill sticky.

[yellowjacket]

I took the empty standard 1/2 gallon BMW bottle with the correct threaded end and cut it off about 1/2" from the bottom. I then took a round empty plastic orange juice bottle and cut it off the same. I then extended the vent tube with a piece of 5/16" ID clear gas line. I then used JD Weld ant glued them together. I now have a 1 gallon container with a threaded cap on one end to fill and correct threads on the other end. Filling active and passive is no longer a problem, fill up new container using 2 1/2 gallon DEF, screw on top cap, screw into car and push. PRESTO.

[335ddd]

after reading the thread I have a few questions.
some people say fill up only active tank but some only passive.

since I drive around 7k a year and DEF fluid has a shelf life of 1 year would it be better to just fill an active tank this way the fluid stays fresh with less chance of crystallizing (my dealer already replaced DEF injector which was clogged) ?

If I am only filling an active tank eventually the passive tank will become empty. Will an empty tank create a future problem due to it being dry such as ruining the transfer pump (between passive/active) because lets say its not being used/lubricated? or maybe some small amount of leftover DEF fluid will eventually crystallize inside the passive tank and in the future if a new fluid gets added to the passive tank it will clog up the transfer pump.

With the passive tank being empty, every time low DEF fluid comes up I just added a gallon or so of DEF fluid to the active tank and after a short drive it resets itself correct (no trip to dealer needed) ? I dont really mind having having a spare quart in the trunk plus the warning message is at 1k miles which gives me enough distance to get home

[rulonger]

Originally Posted by yellowjacket

I took the empty standard 1/2 gallon BMW bottle with the correct threaded end and cut it off about 1/2" from the bottom. I then took a round empty plastic orange juice bottle and cut it off the same. I then extended the vent tube with a piece of 5/16" ID clear gas line. I then used JD Weld ant glued them together. I now have a 1 gallon container with a threaded cap on one end to fill and correct threads on the other end. Filling active and passive is no longer a problem, fill up new container using 2 1/2 gallon DEF, screw on top cap, screw into car and push. PRESTO.

Could you post a picture of your invention?

[Quasimodem]

So in my experience, if you are refilling the small bottle and using that to fill the passive tank (top filler), it does help to jack up the side of the car.

[Persian Whisperjet]

I would recommend doing what montr said. Just buy 2.5 gals, and put it all in the passive tank. That will get you a solid 7,500 miles, and the DEF you put in six months from now will be that much fresher. Also, if you put it all in the passive tank the pumping circuitry will have to work more to move it to the active tank, which is good since the enemy is crystallization and clogging.