What is this noise?

[John336]

S7 Facelift, what is this noise after the engine has been running idle (660rpm) for exactly 5 minutes on gear P or N?
https://youtu.be/GRFTorTzg8U

The noise can also be heard right away without waiting if the idle rpm is raised to over 800rpm (over 1200rpm and engine noise overwhelms it). The frequency of the noise does not change/follow engine RPM.
The noise goes away for exactly 5 minutes if you change the gear to any other position and then put it back to P or N.
There is no noise after a cold start until transmission fluid is approximately at least 30C (86F).

Possible sources that are near where the noise comes from (behind the front left wheel, the noise can't be heard from the right wheel side or engine bay) :
0B5315105R (08/2016 superseded by letters AB) Gearbox oil pump
079121601A Additional coolant pump (Engine Coolant Circulation Pump 2 V178 in the SSP 607)
079965561 Additional coolant pump
079121013R Coolant pump
8K0965567B Coolant pump (Charge Air Cooling Pump V188 in the SSP 607)

There are no error codes and the car works fine, no audible noise when driving.
The failed PCV was replaced on August 2022.

[ItsLarryG]

The only thing I can think of is the evap lines run along the driver side and maybe there is a partial blockage making it whistle. Though it is a weird whistle...any codes or CEL?

The trans oil filter and housing is right around there too...

[John336]

The only thing I can think of is the evap lines run along the driver side and maybe there is a partial blockage making it whistle. Though it is a weird whistle...any codes or CEL?

The trans oil filter and housing is right around there too...

No error codes or CEL.

Could it be the alternator ? Is it near that area?

[ItsLarryG]

The alternator is on the other side. Google Self Study 920223 for the engine training manual to see what all is in that area.

Hard to tell, but is this a whistling noise or a high pitched metallic grinding noise? Does it happen all the time or just when it's cold or hot?

[Alabama]

Bought a S7 2015 with 80k miles. What is this noise when the engine is running idle? The noise can not be heard on top of the engine bay. There are no error codes and the car seems to be working normally.

I have no idea but it doesn't sound good. Was the noise present when you bought the car? If not, did something happen? Does the sound change when you go into gear? With luck, maybe something is just loose and resonating. Hopefully the smart folk here will have ideas.

[John336]

Yeah the noise has been there since I bought the car a week ago.

When the engine is started, the noise is not there for a few minutes, then it gradually starts.
However the noise can be always heard on P or N by raising the engine rpm to the 1k-1,2k range.

Sometimes there's no noise on P or N on idle, but if you wait for a few minutes it will reappear.

Here the noise is not heard on P or N on idle rpm, but when I raise rpm to 1k-1,2k range OR shift to R, D/S or Manual the noise is there:
https://photos.app.goo.gl/tGhmj8s7YyLH4cEx6

Could it be the engine mount? There's a slight vibration you can feel in your seat every few seconds when the engine is idling.

[Alabama]

Could it be the engine mount? There's a slight vibration you can feel in your seat every few seconds when the engine is idling.

Wouldn't a broken engine mount throw a code on VCDS? Do you know any repair history by prior owner?

[John336]

Wouldn't a broken engine mount throw a code on VCDS? Do you know any repair history by prior owner?

Yeah, intake carbon deposits is the likely reason for the slight vibration. The relevant repair history is mentioned on the first post.

[Alabama]

The relevant repair history is mentioned on the first post.

Yes indeed. So all OEM. Turbos replaced in about mid-2018. No exhaust work?

[John336]

Yes indeed. So all OEM. Turbos replaced in about mid-2018. No exhaust work?

Exhaust is in stock condition, apart from https://www.active-sound.eu/en/audi/...ol?language=en

[John336]

The source is still unknown, any guesses? Updated the first post.

[MattyMarkey]

The source is still unknown, any guesses? Updated the first post.

With your latest update, it almost sounds like a potential HVAC blower/motor whine... In all of these videos do you have your heat on? I noticed you did in the last video. Does it make the noise when all accessories are off and idling?

FYSA - you may already know this and just doing it for triage-sake, but it's not good to increase RPMs when in park (specific to the DSG)

[John336]

With your latest update, it almost sounds like a potential HVAC blower/motor whine... In all of these videos do you have your heat on? I noticed you did in the last video. Does it make the noise when all accessories are off and idling?

FYSA - you may already know this and just doing it for triage-sake, but it's not good to increase RPMs when in park (specific to the DSG)

Thanks for the tip about DSG.

Turning HVAC on/off doesn't affect he noise (also the noise can't be heard inside the cabin when the doors are closed so the HVAC motor 4H1820021C is out of the question).
Funny how the noise slightly reacts to changing between N/P/D.

Maybe it's a pump motor or a valve ? Microphone is the best way to pinpoint the source ?

[MattyMarkey]

Thanks for the tip about DSG.

Turning HVAC on/off doesn't affect he noise (also the noise can't be heard inside the cabin when the doors are closed so the HVAC motor 4H1820021C is out of the question).
Funny how the noise slightly reacts to changing between N/P/D.

Maybe it's a pump motor or a valve ? Microphone is the best way to pinpoint the source ?

Roger.

Usually if there is an issue with the secondary pump, it will throw codes pretty quickly. Never say never though lol. Certainly could be a vacuum leak, or what was said previously; evap system issue


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[John336]

Just to confirm: After driving (regardless of the outside temperature, e.g. 14F or even colder) and the engine is turned off, the radiator fans blow at 100% (or near that) for a few minutes, I guess this is perfectly normal ?

[gk1]

Just to confirm: After driving (regardless of the outside temperature, e.g. 14F or even colder) and the engine is turned off, the radiator fans blow at 100% (or near that) for a few minutes, I guess this is perfectly normal ?

I respectfully disagree. I think it is not normal.
When it is that cold the fans may run on shutdown but not usually at 100% unless you are absolutely hammering on the car before shutting it off.
At least that is the way my car has been since new.
Perhaps it is just your perception of what 100% fan sounds like. If you have VCDS you can activate the fans and then you can see what 100% fan sounds like and compare to what you hear.
Now on a hot summer day after some hard driving then sure, near 100% fan can occur after shutdown, but I have not had that happen for light/normal cold weather driving.

[Alabama]

I respectfully disagree. I think it is not normal.
When it is that cold the fans may run on shutdown but not usually at 100% unless you are absolutely hammering on the car before shutting it off.
At least that is the way my car has been since new.
Perhaps it is just your perception of what 100% fan sounds like. If you have VCDS you can activate the fans and then you can see what 100% fan sounds like and compare to what you hear.
Now on a hot summer day after some hard driving then sure, near 100% fan can occur after shutdown, but I have not had that happen for light/normal cold weather driving.

I respectfully agree with your respectful disagreement. Temperatures at night actually can get below 32 degrees in Alabama in the winter. I'm not clever enough to note if the afterrun fan speed is different, but certainly the duration of fan activation is shorter.

[John336]

You were right, I checked with VCDS and the fans were spinning only at 30-40% speed

[John336]

There haven't been any problems associated to this noise, and it can be only heard if you open the door while the engine is idling.

Therefore I'm ignoring this for now, unless someone can pinpoint the source.

[Alabama]

FYSA - you may already know this and just doing it for triage-sake, but it's not good to increase RPMs when in park (specific to the DSG)

Now I'm curious. The DSG has two gear shafts, so either one may be "in gear" or "out of gear". There is also a clutch, so the clutch may be "engaged" or "not engaged". When the transmission is in neutral, what is the state of the clutches and gears? I assume one of the gear shafts is already in first forward gear but the clutch is not engaged. From your comment however I wonder if the clutch is partially engaged so increasing RPMs is the equivalent of "riding the clutch" on a manual transmission. Is that right?

[John336]

So it turns out the noise comes from the PCV, the noise is now much louder and also can be heard during driving.
Lifting up the oil cap removes the noise.

I also have the P227900 intake air system leak DTC.

Any other parts that I'll also need apart from 079103542E ?
The new fixed oil strainer has been installed already in 2018, here's the full part list of that time:

[John336]

As I'm replacing the PCV, should I also replace the oil strainer once again (was changed 4 years ago) ?
How much extra work is it? Engine oil has to be drained but if you change only the PCV that will not be needed?

[John336]

So I ordered the following parts, as listed on the PCV & Oil strainer TSBs:

079129717J seal
079129717K seal
079145818 seal
079103542E oil separator/PCV
079115243C control valve
079115175G oil strainer
079103161Q seal
WHT005529 o-ring 2x
4E0121666 o-ring 2x
N 0138498 engine oil drain plug gasket (N0138157 for some other models, maybe S8)
079198405D engine oil filter element with gasket
N 90303801 o-ring 2x
WHT001011 o-ring
N 90489801 clamp 2x
N 90442501 clamp 2x
N 91130802 nut
N 90409501 ear crimp hose clamp 2x
N 91130802 hexagon collar nut, self-locking
N 10124306 Hexagon socket flat head bolt 10x
engine oil
G13 or G12++ coolant
distilled water

didn't order 079145417B seal (2x) as these can be reused according to the oil strainer 21H7 TSB

[John336]

So the failed PCV was replaced and the big whistling noise while driving disappeared, but the minor noise coming from behind the left front wheel on idle is still there.

I guess it's nothing serious.

[John336]

Updated the first post, maybe it's the gearbox ?

[John336]

Anyone have a clue, what could be the exact 5 minute timer the noise follows?
Perhaps a change in the transmission fluid flow rate initiated by the mechatronics unit?

[John336]

So my local mechanic confirmed the source of the noise is the ATF pump 0B5 315 105 R / AB, and it's perfectly normal.

The noise might get quieter if the OEM VAG ATF oil G 052 529 A2 is used ?
In my case BG 319 ATF was used during the 75k maintenance (18k miles ago).