Hopefully some TDI owners out there can chime in.

During recent undercar inspection I pressed upwards on bottom of the large undercar DEF storage tank and quite to my surprise it moved upwards like it is not anchored or insulated to keep it from moving around. Basically it feels like that tank is just 'floating' right now and the steel straps beneath it are tight. Capacity is around 5 gallons, but mine is nearly empty, so it takes no pressure at all to move the tank around. This seems very odd given the transfer pump, plumbing, etc, surrounding this tank that it should be able to flop around.

Background from work performed on car:

Audi did replace both DEF tanks and everything else to do with my SCR system while under warranty, so my current best-guess is they didn't reinstall some type of insulator material/pad/device on top of the tank during reinstall process. Obviously, when filled with 5 gallons of DEF it's not going to move around too much, but it sure feels rather 'janky' and like something is wrong currently when nearly empty.

Like I said, an Audi dealer tech replaced it, and also during that same warranty visit they actually left the fender liner off the car when returning it to me. I didn't look over the car carefully and got home (3hr drive) to find the fender liner missing...that's a wakeup call right there. Got a lot more serious about doing a thorough walk-around and checking inside car & under hood after that incident.

The fender liner protects/covers up the smaller, working DEF tank & pump system located next to the fuel filler neck, so definitely anything is possible if they managed to leave that big sucker off the car with all the shiny new SCR parts exposed/visible

Thoughts? Did they leave something off the car when installing the new DEF tank, or does everybody's main DEF tank have some 'slack' in it.

Appreciate your taking the time to check yours out for comparison; the main DEF tank is located just in front of the fuel tank on driver's side and has a metal skid plate type protector beneath it, and the support straps go under the metal plate. The fuel tank is not shielded.

TIA!!!

 

I dropped mine when I installed my Darkside delete. It was definitely up there pretty solid. Unfortunately I didn't take any pictures when I had it down and I flushed it with clean water. If I had to guess there was some rigid conforming foam up there, but again, I just don't remember. I'm not in a position to quickly drop it again to check.

Sorry,
Matt

 

Thanks for the reply; you shouldn't need to drop the tank out, as if there were something on top of it you should be able to to either see it visually or physically feel/touch it, etc.

If your empty DEF tank is anchored solidly/and doesn't easily move vertically around like mine is, then that kinda answers the basic question I had. Now it's just down to figuring out what (else) they left off my TDI. Just love that Audi dealer attention to detail. I did get a lot of good work done out of my TDI settlement warranty, but finding stupid stuff like this a few years after they replaced literally every piece of my SCR system simply blows my mind and makes steam shoot out the ears.

Thanks again, and if you do get chance to visually or otherwise confirm an insulator on top of that tank, please follow-up.

Gonna see if I can locate a parts diagram for it.

 

Found a schematic; looks like there are four locating pins on top of the DEF 'passive' tank undercar. Likely those would have some type of rubber insulator that fits over those four molded 'pegs' to keep the tank from moving around. The schematic didn't show any other other insulation layer or mention it for the R&R of this particular tank.

Next step: To the Audi parts catalogue

 

You got me curious. I crawled underneath and there are rubber pins that make contact with floor pan to provide stability and the required offset for hoses/connections.

Best photos I could take.

 

Now that's what I'm talking about...skin in the game.

Thanks for those pics. I don't have those insulators currently, so I'm sure they just took off the old tank and set it aside w/o paying attention to those being required to keep it in place, although you'd expect/think they might've noticed it was loose in the holder after getting the support brackets tightened up...sigh.

Fricking inattentive Audi Techs make me crazy. That warranty on the SCR system was done in Houston, TX and I'm in northern, KS currently, so guess I'm calling Audi of America again. At least I still have their number on speed-dial in my phone. Not that I'd mind popping those in there myself, as I'm two hours drive time from nearest Audi dealer.

And onward we go marching towards resolution...

 

RESOLUTION:

I called nearest Audi dealer parts desk, gave VIN# and described insulator item required for the passive (DEF) tank undercar. I did this just to get the exact part # and verify pricing for them. Took the guy few minutes but he found it described as a 'Sound Insulator' part# 8K0201274B, and listed for only $2.55/each, and this is why we look things up by the VIN# and call the parts counter to verify.

I was about to jump on that and then remembered to ask the shipping charge to deliver (two hour drive to the dealer location, two hours back...nope, not gonna happen!) and quoted me over $20 to deliver them. Said didn't have stock/special order item. I said no thanks, I'll locate some elsewhere.

Part # pasted into internet browser, and then found it's a common parts bin item used by most all VW / Audi vehicles, and VW dealers got it marked down to $1.38/each and only $6 for the shipping to my door...so about $12 all-in delivered.

It'll take maybe half hour required to install them, as my passive DEF tank is nearly empty it'll be easy, and this hidden quality control oversight (courtesy of Audi N. Houston, TX) will be in my rearview mirror.

Let's not forget the service tech at this dealership also forgot to reinstall fender-well liner during same warranty visit, which protects the primary SCR active tank/pump systems, so for all you owners out there still thinking Audi dealer is where you should take your Q7 for 'expert', high-quality service/diagnosis/repair...I'd strongly suggest you not do so.

Appreciate all the help!

Part Number
8K0-201-274-B
Part Name: Fuel Tank Insulator
Price: $1.39 Quantity: 5
Subtotal: $6.95
Estimated Shipping to 66441 via Economy Shipping: $5.08
Total: $12.03

 

Great to know!

On a related note, I've been looking for stations that pump DEF.

Then I did a bit of googling and it seems that buying the jug is *safer*. Less likely for contamination, etc.

I go through two jugs a year. Guess it's not too much effort.

 

Yeah, I thought about filling up the DEF at a truck stop when was out on the road once when the 'Adblue' countdown clock started ticking down, but then remembered reading a lot of threads about SCR problems occurring right after owner filled at one of those or used a sub-par or expired jug of DEF to fill their TDI Q7. Best case your Q7 guzzles the DEF like a maniac as it is either old or lower quality, and worst case you end up with a very expensive repair or 'choice' of how to proceed next, after looking at the expense involved, etc.

DEF has a short-ish shelf life at about a year, so always check the date code on it.

I think it's odd that DEF, like oil products, is sold/marketed in multiple 'grades' of quality. I buy the Peak branded DEF, which claims ultra high purity and multiple certifications, etc., and that works just fine for me. One fill-up gets me through a year, so two 2.5 gal jugs does the trick and costs me about $26 USD. I buy it during a sale or get it from Sam's Club for best price.

I stopped at a Tractor Supply store today and checked price on DEF, and then compared the Peak DEF vs the Peak DEF 'Platinum', upmarket version, which claims to be able to clean deposits inside the SCR system and also magically improve fuel economy. Not sure how it could positively impact fuel economy since it is an emissions aftertreatment/catalyzer. It really does just one thing and that's reduce the amount of NOx exiting the tailpipe. The two NOx sensors are what determines how much DEF/reductant gets sprayed into the exhaust stream. The ingredients lists were the same on both boxes, but the 'platinum' DEF price is about $4 more per box/jug. If they hadn't put on the box that using that product can improve your fuel economy, it might be more believable marketing, but I'm not buying it. The ingredients list and all descriptions of product makeup, the purity, amount of urea vs water amount, etc. was 100% the same on those two boxes.

What I have read is that if you buy/use lower purity of DEF in a Q7 TDI, is that it will use a lot more DEF to achieve the exact same level of NOx reduction, so you aren't saving any money by cheaping out on the store-brand DEF, and may even be creating problems for the SCR system down the line, if not more immediately. A few owners reported getting SCR system fault codes after refilling with store-brand DEF, so this Audi Q7 TDI system desires the 'good stuff' to function properly.

I had entire SCR replaced by Dieselgate settlement warranty, so I'm gonna pay reasonable price for high quality DEF/AdBlue and get on with life.

Don't forget to reset/adapt SCR system after completely filling the AdBlue tanks, and make sure your fuel tank is filled so the AdBlue level warning will reset itself. The fuel tank fill level is a requirement for the miles-to-no restart warning to reset itself, etc., and a lot of owners simply don't know that.