Acuransx

I just came across this on Audizine (B8 board if I recall correctly but concerns the 3.0T engine). From what I read sounds like the S/C is the culprit. I wonder how big a deal it is to remove the S/C belt to see if noise disappears once the S/C is not operational.

https://www.audizine.com/forum/showt...ing-Idle-Noise

TechCom-Mike

Hope you both get an answer soon but doesn't anyone else consider it mind-blowing that a lead tech at an Audi dealer hasn't seen enough in their time to almost instantly diagnose something like this as easy as pie? Are cars just getting way way too complex for their own good? Direct Injection is supposedly a step on from Port Injection but there's all that coking issue on the valves once you're out beyond 60K miles, sometimes sooner. For what? A split second faster response time because after all its critical your 45 minute journey isn't 45 minutes and 37 seconds lets face it! Roll on a solid mass produced electric engine with 400 miles between charge with just less friggin parts - or maybe Tesla, maybe even Audi are there already??

cly7n

any update on this? experiencing the same noise, same miles

Acuransx

I can weigh in on this issue. First, I suggest you take a look at this thread on Audizine: https://www.audizine.com/forum/showt...ing-Idle-Noise -- I'm Acuransx1 over there. Long story short -- I had dealer look into this noise (I have a very good relationship with them and know their lead tech pretty well; service manager too) and they could not figure it out. They did not think anything major but did write up a work order to paper the file in case something lets go down the road. I also took the car to a very well respected indy who similarly could not figure this out and said that everything checked out fine via codes, etc. The advice (which I think was appropriate) from dealer and indy was just drive the car and don't worry about it for now. If something is seriously wrong or headed there, the problem will ultimately make itself known.

Upon the recommendation of my good friend and highly skilled/trusted master Acura tech of 30 years I had a Blackstone oil analysis done. It came back perfect so there is nothing internal in the engine wearing abnormally. I should also add that I corresponded with four or five gents on Audizine who have same issue -- exactly same story as me -- no one who has looked at their cars can figure out what this is. My gut says it is the supercharger and the $64,000 question is whether over the long haul this will get worse/become a problem or remain as it presently is. My car runs perfectly despite this noise which is pretty subtle.

So, in the end, really can't give you (or me) any comfort that this is a non-issue but the good news is that presently aside from the subtle knocking from time to time, no ill effects on performance. I'm not going to throw any money at this issue unless and until it comes very clear exactly what it is and it begins to cause real problems. FWIW, I only intend to keep the car until 65-70,000 miles (I'm at 47,000 now), so hoping that things remain as they are until then.

Best,
Jeff

BLACKTOP_MODS

It is most definitely not the supercharger. We thought the same thing and put in a new one. Same knock. We took the engine out and examined the crud out of it. No apparent issues. No misfires. My Audi mechanic who is also an R8 and Ferrari race mechanic (just to say he's not a run of the mill mechanic) thinks it might be the valve control actuator..so we're going to rip the engine out for the third time. We are determined to figure out what this is! I'm sending my son off to college in this thing so I need to know it is good to go.

Also not the drive shaft, not the transmission as it makes the sound when it's in neutral as well and is 1:1 engine speed. Not the valves and does not click like valves and we checked the valves both times we took it out. I have a lift at home so taking it out while a pain the butt, isn't too painful.

We also sent it out to another reputable German car specialist, they could not figure it out and wanted to put in a new engine (no warranty on the engine)... so that's why we're tearing it down again.

BLACKTOP_MODS

Yeah, it's not the oil separator here. Just for giggles, I went out and tried the test and didn't make a difference.

We also have a g28 (engine speed) disparity with G163 (cam speed) yet no misfires at all. Causes a check engine light. It's got to be the cam adjuster... I checked the rods myself as did my audi mechanic, they are perfect. Also checked valves (just in case, though no one really thought that was it) , perfect. It sounds like rod knock, yet zero play at the crank from the rods.

Acuransx

Update of my 11/30/20 post -- then at 47K miles, now 72K miles. Engine running totally perfect and have almost forgotten the noise that seems to come from back of the supercharger -- slight knock. I'll have to check in next week or so if it is still there. Assuming it is, just one of those things that is not worth worrying about given the 25K miles I've put on car since noticing same. It certainly has not gotten any worse. Could it be the PCV? Maybe. If I keep the car longer than originally anticipated (may hold on until 100-110K miles) when I do the water pump/thermostat/crossover pipe under the s/c and a few other preventative things, I'll replace the pcv and see if noise disappears. I'll post in a week or two and let all know if the subtle noise is still audible.

Again, unless the noise is more than subtle, this is one of those rabbit holes that IMHO is not worth going down.

Best,
Jeff

madman21

Hey Jeff!

Have you changed the PCV yet? And how is your car holding up? I just picked up an A7 with 50k miles and noticed thissame exact sound.

Thanks!

Acuransx

Hey madman so I managed to "work-avoid" all weekend and just hit the office to do what I need to have done for Monday a.m. More work avoidance as I booted up computer and decided to check AW. So glad you reminded me about this. I put the A6 into storage for the winter in a friend's garage hooked to a battery tender. Fired right up last week and I just put 550 miles on it yesterday - quick trip from MI to Toronto. Performed beautifully and 31.8 mpg hand calculated the old school way. I was not in a rush but wasn't going terribly slow -- anywhere between 65 and 75, most of the time at 70 give or take a few.

So car essentially has same miles on it as my post above in September /22. I will check tomorrow to see if that noise is still there. It doesn't sound as if any of our compadres in this thread have experience any engine failures attributable to the mystery noise. Blacktop really went all out on this issue -- if she/he sees this would be great to hear if any conclusive cause for the noise. For my part, I'm just going to drive the car and not worry about this unless it gets louder, if it is still there. Thanks to kelisko for sharing his/her experience. I have not had to change the pcv yet or do the preventative cooling system service but when and if the time comes I will for sure change out the pcv and we'll see what shakes.

I will check on the noise next couple days and report back. In the end I think it is just one of those things that is likely best viewed as a quirk of this engine -- lots of time/money can be spent trying to track something like this down and in my humble opinion not worth doing that unless you are capable of serious wrenching on your own and have the time.

At 72K-ish miles the car seems to be holding up very nicely -- runs and rides pretty much like new and everything works. I did have a complimentary inspection done at dealer when I took it out of storage -- everything good, even battery (which I'll replace soon preventatively since the car will be 8 years old in July) except left rear shock "sweating" just a little. Lead tech said not to worry about it now -- felt it would not be an issue for a year or more and we'll just keep an eye on it.

Best,
Jeff

madman21

Thanks, Jeff!

I'm going to have my indy look at it. Did a ton of research online and it may end up being the flexplate. Will update the thread once I hear back.