[jdub486]

Picked up a 335d a few months ago with 52k miles on the clock. At 55k miles the DEF tank went out, replaced at dealer. It was fully filled when replaced. Stock car. Yes, I have searched and gotten mixed results.

I had some spare time today so I attempted to top off the DEF. The car has 60k miles now. 5k since last fill. The top port (I believe passive) would barely take any DEF. Took only about 2 ounces. Using the BMW screw on half gallon.

The bottom port (I believe active) slurped up the half gallon in no time.

Is it odd that the top port would not take any fluid?

Is it possible when the tank was filled both active and passive were full and the passive tank has not needed to move anything yet to the active?

Could the passive port be clogged already?

[Owen81]

That is odd indeed.
It is possible but you'd have to be hypermiling as I belive it uses urea at a rate of 2-3% of your fuel consumption, which means you should have used at least 3-4 gallons of DEF already at 30 MPG.

Why are you topping it off? Just wait for the no start message (1 gallong of DEF left) then see where its at.

E90 DEF Capacity (Service)
Active 7.4 liters or ~2 gallons
Passive 12.7 liters or ~3.4 gallons

[335dlci]

I haven't topped any of my urea off in probably 25k?

[jdub486]

No hyper-miling. I drive it pretty hard.

It doesn't make any sense that the passive tank would not take any DEF. I will drive another 1k miles and try again.

Any suggestions welcome!

[kbsilver]

Since a software update 4 years ago, my car barely uses any DEF. Before the update it use to trip the 999 miles to no start before each oil change. Because of a DEF tank replacement, I have not added any DEF in all that time. They filled it when the tank was replaced and that was over 20K miles and 2 oil changes ago. I find it hard to believe the car is meeting emissions specs using so little DEF.

[335D Alpha Pappa]

Originally Posted by kbsilver

Since a software update 4 years ago, my car barely uses any DEF. Before the update it use to trip the 999 miles to no start before each oil change. Because of a DEF tank replacement, I have not added any DEF in all that time. They filled it when the tank was replaced and that was over 20K miles and 2 oil changes ago. I find it hard to believe the car is meeting emissions specs using so little DEF.

Was that before or after DieselGate? You might be a test car for BMW copying what VW did.

4 year old DEF is probably a block of crystals.

[Owen81]

Yes that is very odd, and you have no codes?

[kbsilver]

DEF in the tank is about 2 years old. I have no codes, car runs perfectly (102K miles). I mentioned this to the SA several times but always the same answer, no codes = no problems. Best I can tell car is operating about a 0.6% DEF to fuel ratio. All the information suggests this should be between 1-2%. Car is 100% stock, no modifications at all (except shocks). I do hear the DEF transfer pump running from time to time so it is using some.

[335stoner]

if my car doesn't say it needs def i don't worry.

my car has a level issue and the car throws a ses for not knowing where the level is when it gets low.. i stick a gallon in and the ses goes off, i roll on.

[jdub486]

I’ve driven 2k more miles now. So around 7-8k miles since the def tank was replaced and re filled. The passive tank won’t take any def. I’m thinking the passive tank vent may be clogged or pinched? What a pain to go back to the dealer. Active tank takes fluid no problem.

[335dlci]

Sounds about normal. People hate the system but complains when its actually working. Havent filled mine in about 20k

[g335d]

For a couple of years now, I’ve not been able to add to passive tank; I just fill the active when it asks for it, which isn’t often after the above mentioned software update. I refuse to pay $$ to fix it; I suspect that the vent is plugged.

[jdub486]

So, my dealer mechanic tells me now that the top port is the active tank. Bottom is passive. This makes sense as the bottom port took about 1.5 gallon of def after about 7k miles since being filled. The top port stays full or close to full thanks to the transfer pump which you can hear after the car is stopped most of the time. I generally trust this mechanic as he has a diesel e70 x5 and he replaced my active tank and many others at the dealer under warranty.