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4.0TT Turbo Failure Thread - S6 S7 RS7 A8 S8

A8 / S8 (D4 Platform) Discussion Discussion Forum for the D4 Audi A8 Produced from 2010-2017 Audi S8 produced from 2012-2017
View Poll Results: 4.0TT Have your turbos blown yet?
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4.0TT Turbo Failure Thread - S6 S7 RS7 A8 S8

Old 03-21-2019, 09:58 AM
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I wonder has a cleaning agent oil additive ever been tried to breakup and clear the turbo screen deposits?
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Old 03-21-2019, 10:06 AM
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Originally Posted by Verybumpy View Post
I wonder has a cleaning agent oil additive ever been tried to breakup and clear the turbo screen deposits?
I am curious as well... I put in liqui moly engine flush 3 months ago at last oil change. Oil came out black as tar so it definitely was cleaning something. Car has 77k on it. Going in on Tuesday to have oil screen, check valve and separator replaced along with all associated gaskets, etc. Will report back with pictures of oil screen.
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Old 03-21-2019, 11:58 AM
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Originally Posted by Verybumpy View Post
I wonder has a cleaning agent oil additive ever been tried to breakup and clear the turbo screen deposits?
I thought about doing this... run some seafoam through the oil feed tube and then change the oil ~100 miles later... but I never got around to it.
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Old 03-21-2019, 02:57 PM
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Default Changing my (V8) oil fill going forward--now VW Audi 504, not 502

So, parsing through this and thinking about it, I have come to the conclusion I will be using VW 504 spec oil going forward, NOT 502 that is probably the 99%+ Audi norm for gas motors.. BUT, this may or may not apply to you, your car, and oddly/unfortunately even where you live. More below.

In general, I prefer at margin to keep the motor clean from the get go--in any controllable way--rather than get into flushing it or preemptively changing out screens and such in a labor intensive job. I do look forward to any field pictures and such though for folks who opt to do that on a pro active basis. I have also been using 5,000 mile oil cycles, and I bought it at only 3200 miles so have controlled the full maintenance history. Since car remains in the AudiCare pre paid service window, basically I have done a few extra ones "in between" the dealer 10K ones. First that was probably just "new car enthusiast disease," but it has morphed into maintaining a beautiful high power motor where turbo issues have bubbled up. I was also not thrilled when twice on these shorter cycle oil changes, the oil sensor apparently read the oil quality was diminished where preceding fill was by dealer. I only saw it in the deep dive VCDS stuff to reset service intervals when I paid closer attention to the "prior" data being cleared. My last self change was 504 spec. I still have two more dealer AudiCare intervals and will be jawboning next visit for 504 fill, though I suspect it will get blown off. Dealers have 504--which is also 507--but I suspect it is all tied in to keeping costs lower and what Audi USA pays for. Needless to say, I have heard squat about Audi acknowledging the oil fill spec and inconsistencies have anything to do with the turbo issues either.

1. As shipped 4.0T oil fill was apparently 504 spec. All 4.0T's, S8 or A8 (or S7 or S6) were shipped into USA with 504 oil--at least as of 2015 and assuming Audi wasn't pulling yet another stunt with the EPA. 504 oil would give them a better fuel economy result, so I could see why they might play games there, especially in the TDI fraud era. BUT, the deep dive EPA table says they were shipping the 3.0T with the more common 502 spec. EPA 2015 raw data table excerpt is below for those of you who want to see it first person. I included the D4 3.0T too so you can see they did differentiate fill by motor. For laughs I left in the MPG related detail--you can see how they round it; behind the scenes in the spreadsheet they also do some adjusting across all the vehicles to try to downrate the optimistic lab conditions to real world. Data comes from this page BTW: https://www.fueleconomy.gov/feg/download.shtml You download the "Datafile" version for a given year...and put your reading glasses on. I focused on 2015 since I own it. I recall from looking at more recent year data it also showed the 4.0T 504 fill info. Also, 504 is what they would be using in Euro petrol motors in general going back some years now, along with the variable and often longer intervals that rely on various algorithms and sensors to compute. Note the opportunity for more late found/hidden issues here at the manufacturer level, where the home country Vaterland cars and testing are not using the same oil spec as dealers and owners are routinely pouring into them here.

2. Dealer service is probably not 504 spec. Dealers do not seem to use 504 oil, at least not mine under AudiCare. I can see it from the part numbers on the invoices as well as the general spec. As a basic give away, if the fill is listed as a 5W40 it is probably the 502 spec oil, while if it is the 5W30 spec, it is more likely to be the 504 oil. As in, 504 oil is typically 5W30, while there are a variety of viscosities in 502. I can't be categorical given how varied the Audi oil approval listings are, particularly for 502.

3. 504 vs 502 technical advantages. I ran off the comparison graph again from the Lubrizol site that allows some oil spec comparisons. See below. (Higher spider graph results are "better" to be clear). What I did was take the leading German auto specs listed on a bottle of Castrol Professional 5W40 502 oil. That is the common dealer fill AFAIK, uV dye and all. They buy in big barrels though, so harder to really trace. To try to present in best light, I included the BMW and Mercedes specs that are also listed on the bottle. The tool notes though say those cross standards type comparisons (i.e. not just among the VW stds.) may not be representative. If anything, here the BMW and Merc. stds provided "better" results than 502 standing alone. In any case I ran all of these against 504 spec. I tred to use colors to delineate the most important and obvious 502 vs 504 spec differences, even in an oil might actually be higher quality in some ways like the BMW + Merc. specs help draw out. The difference is pretty obvious. Besides no brainers like fuel economy and wear, notice on these "turbo" type issues the areas that are helpful--less sludge, lower piston deposits, etc. Lubrizol tool is here if interested: https://online.lubrizol.com/relperftool/pc.html Discussed in threads on Bob is the Oil Guy forum for technical dive stuff, including nuances in these specs.

4. 504 requires ultra low sulphur gas, which needs to be checked at (USA) state level. The BIG catch: to use a 504 oil, you really need to be sure the gasoline you use is ultra low sulphur. I know CA is and has been for some years. It is also required in Europe, and related to why 504 oils are the norm there for new gas vehicles. It was unique in the USA though, and probably among the reasons Audi USA went slow on calling out the 504 spec in general. My casual understanding and memory is other states were supposed to have cut over to it (mandatorily) by a year or two ago. There are also murky EPA exemptions for small refiners that may go out some years still. But at a state specific level, the information is hard to come by and the deadline was delayed a few times along the way. I'm comfortable it works for me in CA, but would urge others to poke deeper in other states or local gas suppliers to get comfortable there, especially the non-"CARB" ones. That is, the ones not following the CA emissions rules--which is also apparently the tie in elsewhere in the thread to get comfortable the CA emissions warranty out to 7/70 covers the turbos. To anticipate, there is no magic "web list" (or YouTube video...) by state that I came across in the past. With the current EPA and administration uncertainties, the nebulous exemptions for some refiners, as well as history of postponements, in past I found it hard to really nail down. For deeper dive on the fuel compatibility problem, again search the specs and posts on the Bob is the Oil Guy forum. It has occasionally been flagged on AW too, at least in the D3 forum a few times.

As far as cost/price, at first i was able to get Castrol 504 dealer spec oil from audiusaparts in the $7 or $8/qt. range. But they stopped selling oil more recently. Last search turned up ECS as the likely cheapest in $9 range. Ebay ones are typically somewhat over $10 shipped. Thus yes, this is a fair amount more expensive than the 5 qt. jug or other Spring sale Mobil 1 0W-40 or Castrol Euro Formula 502 compliant oils. On the other hand, rounding error against turbo replace cost. I haven't poked recently, but generically an oil lableled "ESP" in the common brands may be a 504 oil, and it will typically be 5W30. You need to look at the labeling or Audi's 504 supplier spec sheet to be sure.

Last edited by MP4.2+6.0; 03-21-2019 at 05:40 PM.
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Old 03-21-2019, 05:06 PM
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Thanks Mp4. Always appreciate your expertise and thoughtful insight. May God bless you to the fourth generation and may you live forever!

Regarding the oil changes, I agree and would recommend 5k or even 3k oil changes. You are fortunate in having loved your baby from infancy however, others have reported loving their 4.0T babies from birth in the same way with 5,000 mile care and their turbos died prematurely anyway. The problem appears to be the design and though I would like to believe extra maintenance or special oil or cleaner would be a solution, the evidence says otherwise. Further disconcerting is that even if we go through the trouble of opening her up and changing the suspected oil screen and check valve with revised parts, the turbos may have already been damaged from improper oiling over the years that they will die prematurely anyway.
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Old 03-22-2019, 09:30 AM
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I think keeping the oil clean, is better than cleaning up after a mess. I started with 5k mile oil/oil-filter changes and have since moved to 3k mile oil/oil-filter changes on my 4.0T.

In the 4.0T engine oil system, the only thing that will clean the oil particulate is the oil filter (trapping), so that should be changed often enough to remove particulate that could clog the turbo oil supply screen. Oil changes (without the filter change) can only dilute any residue fluid/particulate that would not get trapped by the oil filter.

Some people are using the
EPR 109 oil flush EPR 109 oil flush
, it is unknown if the O-rings, gaskets or other seals might be affected by volatile solvents in the EPR. The instructions say to run for 10 minutes at 1200 RPM, then change the oil and oil filter (do not let it cool down too much). The 4.0T oil filter does not get bypassed unless it is clogged or the engine is running over 4k with high oil pressure. One could run the EPR flush with fresh clean oil and new oil filter, then cut open the filter to see what was picked up https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4368489/re-extreme-sludge-305-sbc-engine#Post4368489.

From BG webpage: https://www.bgprod.com/blog/lab-qa-s...in-the-engine/
"BG EPR is designed to remove deposits from components and suspend them in the oil to be removed during the oil change. If BG EPRĀ® is left in the engine for more than the recommended service time, eventually it will evaporate out and re-deposit the heavier oil fractions within the engine. This is especially true if the oil is allowed to cool and the heavier debris separates out."

Some of the unknowns is how the EPR solvents affects the plastic windage tray & the elastomer seals of the bed plate.

From Audi SSP 920223, page Body11 & Body12:

"Engine coolant does not flow through the bed plate. However, it does contain oil passages and galleries to transport pressurized engine oil. The bed plate is sealed to the cylinder block and oil pan by liquid sealant and formed elastomer seals. The oil filter module is integrated in the cylinder block."

"Windage Tray
This tray separates the crankshaft assembly from the oil pan. As a result, the crankshaft webs are not immersed directly in the engine oil. This prevents foaming at high engine rpm. To reduce the weight of the engine, the windage tray is made of plastic."

Many years ago, I would run Redline gas treatment to help clean the high flow injectors on my 91 & 99 Mustangs. Years later, I tired the same Redline gas treatment on my MB AMG C32, but it caused some hoses to fail in the fuel Evap system, so I do not use gas treatment anymore (last time was 2004).
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Old 03-23-2019, 01:29 PM
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2014 S7 with both turbos just replaced at 59k miles. I purchased used at 52k miles in June 2018 and out of warranty ()

I've signed up to a couple of forums today that helped me investigate the issue over the past few weeks - this thread was one I reviewed a few times, so I wanted to give my details, maybe some info will help someone in the future.

Failure history: Car is unmodified. It had been in the Audi servicing network until I bought it - I had oil changes done at my Indy. I had no signs, no noises, CEL or any drop in performance that I could detect. On the fateful day 6 weeks ago, I drove 30 mins on highway (normal speed...) then came to a stop, put in reverse and it stalled. I tried but could not restart. Pushed it into parking space and went into meeting for 1 hour, came out and it started and ran for 20 secs before running rough then stalling, could not restart. Tow truck called. If left overnight, it would start and be ok for 20-30 secs then repeat the rough idling then finally stalling - could not restart unless left several hours. There was no smoke from exhaust, still no strange noises or any indication. VagCom showed zero fault codes. Audi Ann Arbor bore scoped and said bad turbo due to scoring.

Some part numbers just fitted:
079-115-175-G = Strainer
079-145-721 = Turbo
079-145-722 = Turbo
079-103-175-C = Check valve
079-103-542-E = Separator

Here is the old strainer:

Compressor wheels - scoring on inner diameter of housing. Both had slight play in shafts:

Turbine wheels - one ok, one missing:

This cost me just over $10k and took around 7 days for the actual work to be completed (from saying go, to getting the car back). Overall time was longer due to 'negotiations' and overall cost was higher due to rental cars etc.

I was denied 'goodwill' by the regional Audi manager due to "being outside warranty". I had also contacted AOA re: potential goodwill, and the very first phone call went well. Then zero, nada, nothing despite my emails and voicemails. Their communication with me was zero and tbh, although I was not expecting a positive result - this wasted a lot of time (weeks) waiting for expected communication that never came.
Audi Ann Arbor were 'ok' (I was probably $customer of the week) - when I went to pick mine up on Thursday they had just had a 2013 S6 arrive with diagnosis = bad turbos. They reckoned to have seen several 2013 model (S6/S7) and mine was the first 2014.
I am hoping Audi make this an extended warranty situation for us all. But not holding my breath.

I really like this car. A lot. But I will now have to decide whether to: Keep rolling the dice, buy an aftermarket warranty, go find a replacement from another manufacturer that is under warranty or has fewer potential 5 figure bills during low mileage period. I ran an B7 S4 Avant for 10 years up to 200k miles and even though I put over $25k into it for servicing (big one being chain tensioners) - I never felt like it would let me down - I could plan ahead for big jobs. With this S7 I am now not so confident of the quality.

Thanks for all the info others have posted, it helped me navigate this issue better.


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Old 03-23-2019, 04:14 PM
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Some said that turbos are covered part of Emissions warranty, did you try that? You can look previous posts on this thread and you will someone mentioning about this.
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Old 03-23-2019, 05:49 PM
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Originally Posted by Dreamszalone View Post
Some said that turbos are covered part of Emissions warranty, did you try that? You can look previous posts on this thread and you will someone mentioning about this.
7 years, 70K miles, but you need to be in a "CARB" state that follows the CA emissions rules--CA, west coast, Northeast, etc.
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Old 03-24-2019, 04:18 AM
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Originally Posted by MP4.2+6.0 View Post
7 years, 70K miles, but you need to be in a "CARB" state that follows the CA emissions rules--CA, west coast, Northeast, etc.
I did look into Federal Emissions warranty, I was grasping at all straws. California may differ, but for the rest of us (after 2 years, 24k miles) I believe it boils down to the list of components covered and turbos are not one of them:


The Clean Air Act requires manufacturers of light-duty vehicles to provide two federal emission control warranties: (A) "Performance Warranty" and (B) "Design and Defect Warranty." These warranties are provided by the vehicle manufacturer and apply to used vehicles as well. The warranty period begins from the date of sale to the original owner.

The Performance Warranty covers repairs which are required during the first 2 years or 24,000 miles of vehicle use (whichever first occurs) because the vehicle failed an emission test. Specified major emission control components are covered for the first 8 years or 80,000 miles (whichever first occurs). The specified major emission control components only include the catalytic converters, the electronic emissions control unit or computer (ECU), and the onboard emissions diagnostic (OBD) device or computer.

The Design and Defect warranty covers repair of emission control or emission related parts which fail to function or function improperly because of a defect in materials or workmanship for 2 years or 24,000 miles (whichever first occurs), and the specified major emissions control components mentioned above for 8 years or 80,000 miles (whichever first occurs). The manufacturer can deny this warranty coverage if evidence shows that the emission component failure was caused by improper use or maintenance and not caused by a defect.

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