Best way to Maintain your DEF System

[HMBJack]

I have a 2014 Audi TDI with a turbo V6, 58,000 miles.
A few years ago, I had the VW Authorized emissions repair done under warranty already (from the big lawsuit).

Question:
My Mechanic (non VW or Audi) told me the TDI's with DEF systems can have SERIOUS and Expensive issues when they exceed 100,000 miles.
Something to do with contaminates getting into the DEF system that clogs it up somehow. He said when you reach 100K miles, I should sell the car or plan to pay $10K to have the emission system cleaned out and replace certain components.

Have you heard of this?

What do you recommend with respect to maintaining the emissions system on a DEF TDI powered car?
One guy said to keep the DEF tank as full as possible to avoid crystalizing.

Thank you in advance for your advice and comments.

 

[IndigoBlueWagon]

That information is both vague and likely innacurate. First, I doubt the DEF system in your car has $10,000 worth of components. If he's referring to the DPF, catalytic converter, and other emissions system components, that's a different thing. And although they're supported by DEF injection, they're not part of the DEF system.

DEF failures we hear of are usually related to the pump, heater, or the sensor that indicates when you need to add DEF. None of those are terribly expensive. And emissions component life varies depending largely on how the car is used. You should also have an extended emissions warranty with your Qudi (if that's the correct vehicle) that will likely cover you past 100K miles.

Sounds to me like you have a grumpy mechanic.

 

[Mega__Man]

I am part of many forums across my many interests and hobbies, and frankly I can't keep with all the rules, if this does violate any rules on tdi club, I apologize and please remove

I know this thread is starting to age, but I found this when I bought my cummins (still have! ) and it helped me understand def

Source, genos garage, turbo diesel register

Def Myths

There seems to be a fair amount of confusion on the role of DEF in the new trucks. I hear many comments that the system should be removed at the first opportunity because the truck will last longer or get better fuel economy. Both of those are myths.

In my opinion DEF was probably the best thing to happen to our trucks. DEF has one role in the truck’s emissions system—reduce NOx emissions.

Remember, our fire-side chat example: You build a hotter fire (efficient combustion/high power, big torque) and NOx emissions increase. Lower the temperature and NOx is controlled but particulate matter (soot) increases. Diesel exhaust emissions are a delicate teeter-totter.

So, without the DEF system, the only other way to reduce NOx is to make internal engine modifications, changes to the fuel injection system, or dump more EGR gases into the intake. I will take the DEF method any day over the alternatives.

By using DEF, Cummins/Ram engineers are able to maximize injection timing, increase fuel flow (read more power), and reduce EGR by injecting DEF into the exhaust stream. I won’t go into all the chemistry behind it, but the way it is done is by injecting DEF in the exhaust stream ahead of a special Selective Catalyst Reduction (SCR) converter. It looks similar to a DPF, but can be identified by the injector upstream. An injector atomizes and mixes the DEF in the exhaust before entering the SCR and chemically reacting with the precious metals inside to change harmful NOx to harmless nitrogen and water. It really is a great system. But any great system can fall prey to many troubles that give it a bad name. Therefore it is important to give the DEF system the same care and attention you might give to other parts of the truck. The system easily adds a couple thousand dollars of parts to the already complex fuel and emission system. So it is important to take care of it.

Another DEF myth is that some DEF products are better than others. The truth is that all DEF is 32.5% urea with the remainder water. So purchase your DEF anywhere you like, it’s all manufactured the same. The problem lies in the fact that DEF degrades with heat. To put it into perspective the shelf life of DEF is infinite at 32°, 10 months at 95°, and 1 week at 140°. That is why you don’t really want to keep the DEF tank full if you live in a warm climate. It is best to run it down, and refill with fresh, properly stored DEF. When the concentration of urea goes above 32.5% it causes the DEF to crystalize in and around the different parts of the system. Ambient heat around the tank speeds the evaporation of the water. If you go back to the DEF shelf life numbers above, you can see that excessive heat is not kind to your DEF.

The article goes over other things that may apply loosely and not directly to our vehicles as well. Good read. But it definitely goes over best maintenance practices.

 

[ticaf]

Yes, as typical with diesel vehicles, driving it A LOT solves a lot of problems that are common with vehicles that are rarely used, and used for short trips.
For DEF, I'd say fill it less but often to keep it fresh.

 

[Thunder Chicken]

With some heavy equipment that is occasional use, it seemed issues would come from long storage periods and the fluid ‘going bad’. Some shops bought pallets of fluid not realizing it would ‘expire’ especially if kept in an unventilated shed that got hit durning a summer, apparently heat makes the fluid ‘go bad’ even quicker.
So be wary of expiry dates on the fluid, how you may store it and how long it may be in your car for.

 

[Lightflyer1]

IIRC VW specs replacing the fluid completely every two years if it isn't being used or used much. Of course regular use and this isn't necessary. I have timed my use for my driving so that I can always add 5 gals and be near or all the way full when done. This keeps it mostly full all the time, and regular use, uses it enough not to need replacement. About every 8k for me 5 gallons.

 

[Hayze]

Yes, as typical with diesel vehicles, driving it A LOT solves a lot of problems that are common with vehicles that are rarely used, and used for short trips.
For DEF, I'd say fill it less but often to keep it fresh.

wrong Wrong WRONG.
Dont let your def be less than half, otherwise it could get mixed with poor quality def if you fill it at a junky hole in the wall gas station. it can make the emissions system wig out and cause engine cel to come up. Possible engine derate or limp mode if Audi has their cars setup that way.

Also will end up making the def tank crystalize and create buildup, which makes the tank a huge pain in the ass the clean, the def lines, quality def sensor, and the dozer (injector.) or mixer what ever they call it in a Volkswagen or Audi.

Driving a lot does not reduce the issue of emissions failing, maintenance does. Cleaning internal parts such as charge pipes, oil changes, clean fuel, quality def, and Fuel filter changes.

Do not use off brand diesel fuel treatments, I wouldn't recommend anything other than Howes fuel treatment.

 

[IndigoBlueWagon]

I'm probably headed for trouble with both of my cars that use DEF. Since buying it in 2017 I've only added DEF to my BMW once, about 2 years ago. And I bought my GSW (new) about a month after the BMW: the dealer flushed the DEF system before purchase, but I've yet to add any DEF to that car. 14K on it so the tank is probably pretty low, at least.

 

[oilhammer]

Biggest issues I have seen regarding SCR isn't the DEF itself, it is all the sensors, heaters, pumps, etc. that fail. In theory it is a good thing, being a post-combustion NOx reducing tool. It allows a diesel engine to better do what a diesel engine is meant to do in the first place: run LEAN, which is why they are so fuel efficient. And running leaner more of the time means less PM, so less DPF regens, and less EGR use.

I just wish the durability of the components was better. And I think they are getting better... sadly we'll never get to experience much of that improved durability here.

 

[Mega__Man]

wrong Wrong WRONG.
Dont let your def be less than half, otherwise it could get mixed with poor quality def if you fill it at a junky hole in the wall gas station. it can make the emissions system wig out and cause engine cel to come up. Possible engine derate or limp mode if Audi has their cars setup that way.

Also will end up making the def tank crystalize and create buildup, which makes the tank a huge pain in the ass the clean, the def lines, quality def sensor, and the dozer (injector.) or mixer what ever they call it in a Volkswagen or Audi.

Driving a lot does not reduce the issue of emissions failing, maintenance does. Cleaning internal parts such as charge pipes, oil changes, clean fuel, quality def, and Fuel filter changes.

Do not use off brand diesel fuel treatments, I wouldn't recommend anything other than Howes fuel treatment.

If you were to read my source you would see why your wrong. About def.

Def is def (assuming it meets government standards which all in U.S. does. Can't say anything else about elsewhere ). And it does go bad over time based off temp. Quality has nothing to do with it. Water evaporation does.

Fuel treatment is open to discussion as well. But you can also make an argument about no fuel treatment. There is no right answer.

 

[ticaf]

wrong Wrong WRONG.
Dont let your def be less than half, otherwise it could get mixed with poor quality def if you fill it at a junky hole in the wall gas station. it can make the emissions system wig out and cause engine cel to come up. Possible engine derate or limp mode if Audi has their cars setup that way.

Do you have any evidence that DEF at truck gas stations is any bad considering all the trucks that go through ??

Driving a lot does not reduce the issue of emissions failing, maintenance does. Cleaning internal parts such as charge pipes, oil changes, clean fuel, quality def, and Fuel filter changes.

Driving a lot, and particularly getting the engine up to operating temperature, and staying there, allows you to put more miles on the car before failure. In fact, if you would start the engine, and only stop it for maintenance (oil changes, etc.), and run it on the highway 24/7, you would get the best MTTF, meaning you get the most miles out of the car before something fails. (by the way, that also applies to gasoline engines. and probably not to EVs).

 

[Lightflyer1]

Driving a lot does reduce emissions failures caused by not letting regens complete. Probably most of the cause of dpf issues in my opinion. Most owners seem to be fairly ignorant of what needs to happen in order to keep it happy. Not the only reasons though.

 

[IndigoBlueWagon]

Driving a lot does reduce emissions failures caused by not letting regens complete. Probably most of the cause of dpf issues in my opinion.

People have been fretting about this for years, but I've never seen any data that supports the idea that interrupting regens is bad, as long as one gets completed once in a while.

 

[Lightflyer1]

People have been fretting about this for years, but I've never seen any data that supports the idea that interrupting regens is bad, as long as one gets completed once in a while.

Exactly what I am talking about. Some drive in such a way that they never complete and set the light, and off to the dealer. As long as they complete when needed all should be good.

 

[TurboABA]

I try to drive mostly at night..... when regens are sleeping.... this way, I reduce the DPF related problems I experience.

 

[Hayze]

Do you have any evidence that DEF at truck gas stations is any bad considering all the trucks that go through ??

Yes as a matter of fact because i been a truck driver the last 5 years, I can tell you that Loves in places such as Midland TX has history with low quality def, and can cause trucks to trigger "engine derate" messages in peterbilt 579's with cummins, and "poor quality def" alerts in Peterbilt 389's with paccar engines.

The reason I mention keeping tank half or above, is so that if by chance you fill at a pump with diluted, contaminated, or watered down def fluid. If because you fill the tank with bad def and the tank was low, it wont be able to mix with the better contents of the def and reduce or avoid issues down the road.

Trucks have been on side of the highway due to filling up a very low def tank with bad def, and the quality def sensors in the def tank on trucks will derate a truck. Which will end up dropping power down to as little as 10 miles an hour, and no miles an hour if your trying to climb a hill loaded.

Now semi trucks and TDI cars are a night and day difference, completely different companies, manufactures, etc.
However i will say that def is def, emissions is emissions, 98% of the emissions equipment is the same, just built in different shapes, placement, and size.

I mentioned these 2 types of trucks in this long comment because of my experiences with them, what i have witnessed, and also witnessing what mechanics do at a shop when it comes to def and emissions related issues.

 

[Hayze]

And it does go bad over time based off temp. Quality has nothing to do with it. Water evaporation does.

Allow me to show you what trucks say on dash message when it detects poor quality def, if i understand your comment correctly.

 

[TurboABA]

Most TDI users will fill up their DEF from sealed 1/2 gal or 2.5 gal containers, not from pumps or bulk containers like the heavy industry relies on.
As such, contamination or "quality tampering" is NOT a thing in our community.
Whatever APU sells you from his leaky tanks at Kwik-E-Mart that's contaminated or taking on ground water is a totally different animal.

 

[oilhammer]

Yep, folks here are typically using DEF from sealed containers. Sure, there are some uber-cheapskate George Constanza types here that WILL find a bulk pump somewhere to save thirty cents, but most will not. So it is a non-issue for us.

Good information to share about poor quality bulk DEF though. Something to be aware of.

Also, I like the odometer in the pic.... almost as much as my Golf.

 

[ticaf]

That's a bummer about DEF quality. My fuel station is less than a mile from home and serves both truck and passenger cars with Diesel, and also has DEF at the pump (truck pumps only though). It is indeed cheaper, but also convenient. 136k miles on that DEF, and the car have been happy so far.

How common is bad DEF vs bad diesel ? I find it hard to believe trucking customers would keep going back to a fuel station if they get poor quality.

 

[Mega__Man]

Sigh. Yea, truck stops ruin def to kill trucks.
I mean they don't need or want customers do they?


Correlation does not equal causation

I have been filling for many a moon without issue At truck stops when I need pulling my rv.

I know what def sensors are ( ram switched to using them after 2016, either 2017 or 18. ) and idk about vw. But the sensors had been just as faulty as anything. Either way, there's a reason I linked to a well known quality site and not just using my own experian or the old saying of "trust me in an engineer" .... everyone will deal with bad things in their life ( Whether or not you call it luck ) I have also filled with bad fuel. Does that mean all fuel stations are bad? Or maybe it was a bad load, batch, supply ect...

Also why I chose that link. It is very informative as to the science behind def

I won't make decisions for you, I will give you my advice and knowledge

 

[Hayze]

How common is bad DEF vs bad diesel ? I find it hard to believe trucking customers would keep going back to a fuel station if they get poor quality.

Its not very common, however if the tank is underground by pumps (if its cracked) and when it rains it will wash into the tank and get diluted. (Watered down)
Its usually what triggers those poor quality messages.
Used to be able to get by with just taking a garden hose and putting water in def tanks, but now California stepped their game up and caught on to those who did this and long story short quality control sensors are in the tanks.
trucking customers dont go back to the same fuel station constantly so its a hit and miss. Does def at pumps do not happen often though.

Most TDI users will fill up their DEF from sealed 1/2 gal or 2.5 gal containers, not from pumps or bulk containers like the heavy industry relies on.
As such, contamination or "quality tampering" is NOT a thing in our community.
Whatever APU sells you from his leaky tanks at Kwik-E-Mart that's contaminated or taking on ground water is a totally different animal.

Sometimes it happens, it could be a lean mixture of def in a big batch, so the whole shelf at the store has bad def.