3.0T Vacuum System Question

**christianb5s4** · 12-27-2019 03:26 PM

All, quick question on the C6 3.0T. I'm trying to find the right vacuum line or lines that can be used to smoke test the vacuum system for leaks? Been searching for a lead on this but haven't found anything concrete.

**CrzyAznKB** · 12-27-2019 08:30 PM

I would pull the line off the mechanical vacuum pump off the front of the engine on the other side of the one way check valve.

**christianb5s4** · 12-30-2019 09:21 AM

I'll give that a shot, believe I've tried it before but will do it again. Thanks for the help!

**christianb5s4** · 01-02-2020 10:52 AM

Found the diagram on 7zap: https://audi.7zap.com/en/usa/audi+a6.../1/133-133052/

Here's the actual schematic, digging for more detail on the EVAP system now but I think my EVAP small leak code is a solenoid issue not a leak in the lines or fittings as I can clear the code (while the car is off) but the code immediately comes back, indicating it's something electrical that has failed.

**11A6** · 01-02-2020 07:34 PM

Interesting as when I use my friends VCDS I've had a small evap leak code but intermittently and I've not had the time nor has it been enough of a problem to track down so far. Will be interested to see what you find,,, might borrow his VCDS this weekend to see if my code is back and if it clears as well.

**christianb5s4** · 01-03-2020 09:01 AM

I've had that same code come back randomly for the entire time I've owned the car. Sometimes it'll go away for months on end then suddenly come back, only to go away at some point again. I ordered new valves 5 and 6 on the diagram as those are the only things that could possibly be left.

Based on the fact the code comes and goes, along with the fact it comes back instantly sometimes when I clear it and the car is off, I strongly believe one or more of those valves might be getting stuck open which is why the system sees a leak. Car runs perfectly otherwise and fuel trims are within spec.

**11A6** · 01-08-2020 07:23 PM

So I was not able to borrow my friends VCDS and tonight in the way home as I realized I have to get the car inspected next month - and I live in the one county in Maine that had emission testing- my check engine light comes on - my rudimentary OBD showed the IMG_5860.JPG. Seems like we maybe chasing the same gremlin - VCDS this weekend and see what else I can figure out.

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**11A6** · 01-08-2020 09:47 PM

One more thing I saw on Ross -tech and not sure if you are aware of it - http://wiki.ross-tech.com/wiki/index...0/P0456/001110

Audi A6/A7/A8 (4G/FC/4H) models with 3.0 TFSI and 4.2 FSI gas engines. When this DTC is stored see if this NAR market TPI applies to the vehicle in question: 2027732. That is a flash update to correct a software problem with specific Engine controller part number(s) in addition to replacement of PCV parts when applicable. If the software was already up to date, J909 or G400 may need to be replaced. See the next note related to those components.

**christianb5s4** · 01-09-2020 10:44 AM

Yup, that's the exact code I have and it's been ridiculously hard to fix. basically at my whits end with this car particularly because it now has an oil leak just after I had a coolant leak repaired and will likely get rid of it in the next few months. I have already done the following to no avail:

- Smoke/pressure tested all lines multiple times
- Latest PCV and Audi software update
- New leak detection pump, new purge valve, new vacuum pump, new secondary air injection pumps, new charcoal canister, etc.
- New gas cap

That said new solenoids 5 and 6 above will be going in the car tonight as those are literally the only thing left related to the EVAP/vacuum system left I haven't replaced. Will report back, but to me my issue seems to be electrical as I clear the code and it immediately comes back even with the car off.

It doesn't look like our cars have the J909/G400 part based on my research.

**11A6** · 01-09-2020 05:55 PM

Ok let me know how it goes - this is only the 2nd time the code has come up. tomorrow I'll fill gas tank and see if that fixes it or not for me. I agree that an electrical gremlin makes sense to be the cause for you - good luck.

**christianb5s4** · 01-10-2020 08:05 AM

Of course even though I paid for 2 day shipping when it shipped on Monday and the solenoids still aren't here, thanks USPS. Will keep you posted.

**christianb5s4** · 01-13-2020 08:56 AM

No luck so far, the code came back as pending (not a set CEL yet) despite changing out those solenoids. Car has also developed an oil leak so it's officially going bye bye in the next month or two. Wish I could have resolved this 2 year long EVAP saga but it's not going to happen.

**B. Rock** · 01-13-2020 01:42 PM

Damn, that's tough. I can understand the frustration since you've been wrestling with that code for a long time and throw a lot of time and parts at it. It sure seems like there isn't anything else to go wrong at this point, but clearly something just isn't quite right.

**jbain2** · 01-13-2020 02:55 PM

Christian, I wouldn’t expect a B5 owner to give up. Oil leaks and a CEL. It’s the way of the Audi!

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**christianb5s4** · 01-13-2020 04:50 PM

Don't get me wrong, I do like this car a lot for what it is. These constant problems despite doing everything right is never ending and has totally worn off any last luster I might have had for the car. It's a real shame, it's a great car for what it is but I can't justify putting another dime into it when I'm in the position to buy something much newer and nicer (and not a never ending problem child).

Touche on the B5 joke lol, but ironically my B5 has been significantly more reliable than the A6. Knock on wood!

**11A6** · 01-13-2020 05:53 PM

Damm that's tough to hear (and worse for you). I can understand your frustration and decision to move on. It seems like the only thing left is whether the monitoring system itself has a bug/flaw that's causing it to say there is a defect when everything working as it should and is new/replaced. I cleared mine and it's not come back after 3 days so I"m still left wondering what triggered it. that's amazing that your B5 has been more reliable. Good luck with your next car.

**christianb5s4** · 01-14-2020 08:31 AM

I've gotten two years and 20K miles out of it so can't complain too much, was planning on keeping it much longer hence why I've put $7K or so into doing every preventative maintenance and attempted EVAP fix possible but such is life! Will do a few road trips this month then February picking up a 2016+ C7.5 A6 or S6 Prestige mostly likely.

You win some you lose some. The main issue though is the oil consumption and the fact it smokes during long downhills which is not a PCV thing as that's all brand new, it's a serious piston ring issue (oil also smells strongly of fuel even with 500 miles on fresh Motul). So long term it's not a keeper.

**jibo1971** · 01-15-2020 06:25 AM

So have you fixed it? And what was the problem i have issue about my 3.0tfsi sometimes fuel is rich sometimes it lean when its hot rpm drops very slow,car has no leaks

**11A6** · 01-15-2020 07:41 AM

Originally Posted by christianb5s4

I've gotten two years and 20K miles out of it so can't complain too much, was planning on keeping it much longer hence why I've put $7K or so into doing every preventative maintenance and attempted EVAP fix possible but such is life! Will do a few road trips this month then February picking up a 2016+ C7.5 A6 or S6 Prestige mostly likely.

You win some you lose some. The main issue though is the oil consumption and the fact it smokes during long downhills which is not a PCV thing as that's all brand new, it's a serious piston ring issue (oil also smells strongly of fuel even with 500 miles on fresh Motul). So long term it's not a keeper.

So mine is a 11 and I bought it used with the same hopes/expectations - I'm kind of hoping they improved the rings as I seem to recall some of the first year cars seeming to have ring issues. I know I need to do the valve cover gasket & carbon cleaning so likely to update PCV while it's apart. Like you I don't want to sink more $ into if if I have the same road ahead. I have some oil above 1-2 plugs but not a lot and the oil consumption is a mystery. Can go 5k 7 be down barely 1/2 a qt and other times I'm down a full qt in 1500 miles. Seems to vary based on oil weight, cold vs. warm season and driving style but I've not been able to nail down the variables.

Otherwise I love the car, the functionality of the wagon etc. Good luck with the C7.5 - looks like a nice upgrade which ever one you choose. Appreciate you sharing your efforts - helpful.

**christianb5s4** · 01-15-2020 09:17 AM

Originally Posted by jibo1971

So have you fixed it? And what was the problem i have issue about my 3.0tfsi sometimes fuel is rich sometimes it lean when its hot rpm drops very slow,car has no leaks

Nope, I replaced those solenoids with no change. The code doesn't come back immediately now but it still comes back eventually. Is your car throwing any EVAP or lean/rich related codes?

Originally Posted by 11A6

So mine is a 11 and I bought it used with the same hopes/expectations - I'm kind of hoping they improved the rings as I seem to recall some of the first year cars seeming to have ring issues. I know I need to do the valve cover gasket & carbon cleaning so likely to update PCV while it's apart. Like you I don't want to sink more $ into if if I have the same road ahead. I have some oil above 1-2 plugs but not a lot and the oil consumption is a mystery. Can go 5k 7 be down barely 1/2 a qt and other times I'm down a full qt in 1500 miles. Seems to vary based on oil weight, cold vs. warm season and driving style but I've not been able to nail down the variables.

Otherwise I love the car, the functionality of the wagon etc. Good luck with the C7.5 - looks like a nice upgrade which ever one you choose. Appreciate you sharing your efforts - helpful.

That's how my car is in terms of inconsistent oil burning, no rhyme or reason I can tell. These 3.0Ts are mostly bulletproof but unfortunately it seems mine is just a lemon through neglect of previous owners and reliability issues dating way back to 2012 based on dealer reports on Carfax. Don't forget that beyond oil burning, my car also smokes like hell under long downhills when the car is under vacuum for a while. That's not normal.

The plus side is you have an avant and a later C6.5 so you should be golden! The avants have really been holding their value well and perhaps might appreciate slightly over time as well.

**jibo1971** · 01-15-2020 12:22 PM

No my car has no fault codes when i adapted car to lamda adaptations in process i think it see s misfires and has detonations but after adaptation car has no misfires it may throw code after adapt system sometimes rich sometimes lean, car problem is when it gets hot RPM comes very slow on idle